This redistribution has happened in the past various times. But in the western hemisphere only 3 of these branches/forks of MySQL are of relevance for the majority of the MySQL users: Galera Cluster for MySQL, MariaDB (Server and Galera Cluster) and Percona Server (and XtraDB Cluster).
Now it happened what has to happen in nature: The different branches/forks start to diverge (following the marketing rule: differentiate yourself from your competitors). The biggest an most important divergence happens now between MySQL and MariaDB.
Recently a customer of FromDual claimed that there is no more progress in the MySQL Server development whereas the MariaDB Server does significant progress. I was wondering a bit how this statement could have been made. So I try to summarize the New Features which have been added since the beginning of the separation starting with MySQL 5.1.
It is important to know, that some parts of MySQL code are directly or in modified form ported to MariaDB whereas some MariaDB features were implemented in MySQL as well. So missing features in MariaDB or improvements in MySQL can possibly make it sooner or later also into MariaDB and vice versa. Further both forks were profiting significantly from old MySQL 6.0 code which was never really announced broadly.
Further to consider: Sun Microsystems acquired MySQL in January 2008 (MySQL 5.1.23 was out then and MySQL 5.2, 5.4 and 6.0 were in the queue) and Sun was acquired by Oracle in January 2010 (MySQL 5.1.43, MySQL 5.5.1 were out, MySQL 5.2, 5.4 and 6.0 were abandoned and MySQL 5.6 was in the queue).
  
    | MySQL 5.1 | MariaDB 5.1 (link), 5.2 (link) and 5.3 (link) | 
  
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        PartitioningRow-based replicationPlugin APIEvent scheduler.Server log tables.Upgrade program mysql_upgrade.Improvements to INFORMATION_SCHEMA.XML functions with Xpathsupport. | MariaDB 5.1 
        Storage Engines
          
            Aria (Crash-safe MyISAM)XtraDB plugin (Branch of InnoDB)PBXT (transactional Storage Engine)FederatedX (replacement for Federated). 
        Performance
          
            Faster CHECKSUM TABLE.Character Set conversion improvement/elimination.Speed-up of complex queries using Aria SE for temporary tables.Optimizer: Table elimination. 
        Upgrade from MySQL 5.0 improved.Better testing.Microseconds precision in PROCESSLIST. MariaDB 5.2 
        Storage Engines
          
            OQGRAPH (Graph SE)SphinxSE (Full-text search engine) 
        Performance
          
            Segmented MyISAM key cache (instances)Group Commit for Aria SE 
        Virtual columnsExtended user statisticsStorage Engine specific CREATE TABLEEnhancements to INFORMATION_SCHEMA.PLUGINStable MariaDB 5.3 
        Performance
          
            Subquery Optimization
              
                Semi-join subquery optimizationsNon-semi-join optimizationsSubquery CacheSubquery is not materialized any more in EXPLAINOptimization for derived tables and views
              
                No early materialization of derived tablesDerived Table Merge optimizationDerived Table with Keys optimizationFields of mergeable views and derived tables are involved in optimizationDisk access optimization
              
                Index Condition Pushdown (ICP)Multi-Range-Read optimization (MRR)Join optimizations
              
                Block-based Join Algorithms: Block Nested Loop (BNL) for outer joins, Block Hash Joins, Block Index Joins (Batched Key Access (BKA) Joins)Index Merge improvements 
        Replication
          
            Group Commit for Binary LogAnnotation of row-based replication events with the original SQL statementChecksum for binlog eventsEnhancements for START TRANSACTION WITH CONSISTENT SNAPSHOTPerformance improvement for row-based replication for tables with no primary key  
        Handler Socket Interface included.
        HANDLER READworks with prepared statementsDynamic Column support for Handler Interface
        Microsecond supportCASTextendedWindows performance improvementsNew status variablesProgress reports for some operationsEnhanced KILLcommand | 
    | MySQL 5.5 (link) | MariaDB 5.5 (link) | 
  
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        InnoDB
          
            InnoDB Version 5.5Default storage engine switched to InnoDB.InnoDB fast INDEX DROP/CREATEfeature added.Multi-core scalability. Focus on InnoDB, especially locking and memory management.Optimizing InnoDB I/O subsystem to more effective use of available I/O capacity. 
        Performance
          
            MySQL Thread Pool plugin (Enterprise) 
        Security
          
            MySQL Audit plugin (Enterprise)MySQL pluggable authentication (Enterprise) for LDAP, Kerberos, PAM and Windows login 
        Replication
          
            Semi-synchronous replication. 
        Partitioning
          
            2 new partition types (RANGE COLUMNS, LIST COLUMNS).TRUNCATE PARTITION. 
        Proxy UsersDiagnostic improvements to better access execution an performance information including PERFORMANCE_SCHEMA, expandedSHOW ENGINE INNODB STATUSoutput and new status variables.Supplementary Unicode characters (utf16, utf32, utf8mb4).CACHE INDEXandLOAD INDEX INTO CACHEfor partitioned MyISAM tables.Condition Handling: SIGNALandRESIGNAL.Introduction of Metadata locking to prevent DDL statements from compromising transactions serializability.IPv6 SupportXML enhancement LOAD_XML_INFILE.Build chain switched to CMake to ease build on other platforms including Windows.Deprecation and remove of features. | 
        Storage Engines
          
            SphinxSE updated to 2.0.4PBXT Storage Engine is deprecated. 
        XtraDB
          
            MariaDB uses XtraDB 5.5 as compiled in SE and InnoDB 5.5 as plugin.Extended Keys support for XtraDB 
        Performance
          
          Thread pool pluginNon-blocking client API Library 
        Replication
          
            Updates on P_S tables are not logged to binary log.replicate_*variables are dynamically.Skip_replicationoption 
        LIMIT ROWS EXAMINEDNew status variables for features.New plugin to log SQL level errors. | 
  
    | MySQL 5.6 (link) | MariaDB 10.0 (link) | 
  
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        InnoDB
          
            InnoDB Version 5.6InnoDB full-text search.InnoDB transportable tablespace supportDifferent InnoDB pages size implementation (4k, 8k, 16k)Improvement of InnoDB adaptive flushing algorithm to make I/O more efficient.NoSQL style Memcached API to access InnoDB data.InnoDB optimizer persistent statistics.InnoDB read-only transactions.Separating InnoDB UNDO tablespace from system tablespace.Maximum InnoDB transaction log size increased from 4G to 512G.InnoDB read-only capability for read-only media (CD, DVD, etc.)InnoDB table compression.New InnoDB metadata table in INFORMATION_SCHEMA.InnoDB internal performance enhancements.Better InnoDB deadlock detection algorithm. Deadlock can be written to MySQL error log.InnoDB buffer pool state saving and restoring capabilities.InnoDB Monitor dynamically disable/enable.Online and in-place DDL operations for normal and partitioned InnoDB Tables to reduce application downtime. 
        Optimizer
          
            ORDER BYnon-index-column for simple queries and subqueriesDisk-Sweep Multi-Range Read (MRR) optimization for secondary index/table access to reduce I/OIndex Condition Pushdown (ICP) optimization by pushing down the WHEREfilter to the storage engine.EXPLAINalso works for DML statements.Optimizing of subqueries in derived tables (FROM (...)) by postponing or indexing derived tables.Implementation of semi-join and materialization strategies to optimize subquery execution.Batched Key Access (BKA) join algorithm to improve join performance during table scanning.Optimizer trace capabilities. 
        Performance Schema (P_S)
          
            Instrumentation for Statements and stagesConfiguration of consumers at server start-upSummary tables for table and index I/O and for table locksEvent filtering by tableVarious new instrumentation. 
        Security
          
            Encrypted authentication credentialsStronger encryption for passwords (SHA-256 authentication plugin)MySQL User password expiration.Password validation plugin to check password strengthmysql_install_dbcan create secure root password by defaultcleartext password is not written to any log file any more.MySQL Firewall (Enterprise) 
        Replication
          
            Transaction based replication using global transaction identifiers (GTID)Row Image Control to reduce binary log volume.Crash-safe replication with checksumming and verifying.IO and SQL thread information can be stored in an transactional table inside the DB.MySQL binlog streaming with mysqlbinlogpossible.Delayed replicationParallel replication on schema level. 
        Partitioning
          
            Number of partitions including subpartitions increased to 8192.Exchange partition with a normal table.Explicit selection of specific partiton is possible.Partition lock prunining for DML and DDL statements. 
        Condition handling: GET DIAGNOSTICSandSET DIAGNOSTICSServer defaults changes.Data types TIME,DATETIMEandTIMESTAMPwith microsecondsHost cache exposure and connection errors status information for finding connection problems.Improvement in GIS functions.Deprecation and remove of features. | 
        Storage Engine
          
            Cassandra Storage EngineConnect Storage EngineSequence Storage EngineBetter table discovery (FederatedX)Spider Storage EngineTokuDB Storage EngineMroonga fulltext search Storage Engine 
        XtraDB
          
            XtraDB Version 5.6Async commit checkpoint in XtraDB and InnoDBSupport for atomic writes on FusionIO DirectFS 
        Replication
          
            Parallel ReplicationGlobal Transaction ID (GTID)Multi Source Replication 
        Performance
          
            Subquery Optimization (EXISTStoIN)Faster UNIQUE KEYgenerationShutdown performance improvement for MyISAM/Aria table (adjustable hash size) 
        Security
          
            RolesMariaDB Audit Plugin 
        Optimizer
          
            EXPLAINfor DML StatementsEngine independent table statisticsHistogram based statisticsQUERY_RESPONSE_TIMEpluginSHOW EXPLAINfor running connectionsEXPLAINin the Slow Query Log 
        Per thread memory usage statisticsSHOW PLUGINS SONAMESHUTDOWNcommandKilling a query by query id not thread id.Return result set of delete rows with DELETE ... RETURNINGALTER TABLE IF (NOT) EXISTSCREATE OR REPLACE TABLEDynamic columns referenced by nameMultiple use locks (GET_LOCK) in one connectionBetter error messagesNew regular expressions (PCRE) REGEXP_REPLACE,REGEXP_INSTR,REGEXP_SUBSTRMetadata lock information in INFORMATION_SCHEMAPriority queue optimization visibilityFLUSH TABLE ... FOR EXPORTflushes changes to disk for binary copyCURRENT_TIMESTAMPasDEFAULTforDATETIMEVarious features backported from MySQL 5.6 | 
  
    | MySQL 5.7 (link) | MariaDB 10.1 (link) | 
  
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        InnoDB
          
            InnoDB Version 5.7VAR CHARsize increase can be in-place in some cases.DDL performance improvements for temporary InnoDB tables (CREATE DROP TRUNCATE, ALTER)Active InnoDB temporary table metadata are exposed in table INNODB_TEMP_TABLE_INFO.InnoDB support spatial data type (GIS, DATA_GEOMETRY)Separate tablespace for temporary InnoDB tables.Support for InnoDB Full-text parser plugins was added.Multiple page cleaner threads were added.Regular an partitioned InnoDB tables can be rebuilt using online in-place DDL commands (OPTIMZE, ALTER TABLE FORCE)Automatic detection, support and optimization for Fusion-io NVM file system to support atomic writes.Better support for Transportable Tablespaces to ease backup process.InnoDB Buffer Pool size can be configured dynamically.Multi-threaded page cleaner support for shutdown and recovery phase.InnoDB spatial index support for online in place operation (ADD SPATIAL INDEX)InnoDB sorted index builds to improve bulk loads.Identification of modified tablespaces to increase crash recovery performance.InnoDB UNDO log truncation.InnoDB native partition support.InnoDB general tablespace support for databases with a huge amount of tables.InnoDB data at rest encryption for file-per-table tablespaces. 
        Performance
          
            EXPLAINfor running connections (FOR CONNECTIONS)Finer Control of optimizer hints. 
        Security
          
            Old password support has been removed.Automatic password expiry policies.Lock and unlock of accounts.SSL and RSA certificate and key file generation.SSL enabled automatically if available.MySQL will be initialized secure by default (= hardened)STRICT_TRANS_TABLES sql_modeis now enabled by default.ONLY_FULL_GROUP_BY sql_modemade more sophisticated to only prohibit non deterministic query. 
        Replication
          
            Master dump thread was refactored to improve throughput.Replication Master change without STOP SLAVE.Multi-source replication introduced. 
        Partitioning
          
            HANDLERstatement works now on partitioned tables.Index Condition Pushdown (ICP) works for partitioned InnoDB and MyISAM tables.ALTER TABLE EXCHANGE PARTITION WITHOU VALIDATIONis possible to improve performance of exchnage. 
        Native JSON support
          
            Data type JSON.JSON functions: JSON_ARRAY, JSON_MERGE, JSON_OBJECT, JSON_CONTAINS, JSON_CONTAINS_PATH, JSON_EXTRACT, JSON_KEYS, JSON_SEARCH, JSON_APPEND, JSON_ARRAY_APPEND, JSON_ARRAY_INSERT, JSON_INSERT, JSON_QUOTE, JSON_REMOVE, JSON_REPLACE, JSON_SET, JSON_UNQUOTE, JSON_DEPTH, JSON_LENGTH, JSON_TYPE, JSON_VALID 
        System and status variables moved from INFORMATION_SCHEMAtoPERFORMANCE_SCHEMA.Sys Schema created by default.Condition handling: GET STACKED DIAGNOSTICSMultiple triggers per event are possible now.Native logging to syslog possible.Generated Column support.Database rewriting in mysqlbinlog.Control+C in mysql client does not exit any more but interrupts query only.New China National Standard GB18030 character set.RENAME INDEXis online inplace without a table copy.Chinese, Japanese and Korean (CJK) full-text parser implemented (ngram MeCab full-test parser plugins).Deprecation and remove of features. | 
        XtraDB
          
            Allow up to 64K pages in InnoDB (old limit was 16K).Defragmenting InnoDB Tablespaces improved which uses OPTIMIZE TABLEto defragment InnoDB tablespaces.XtraDB page compression 
        Performance
          
            Page compression for FusionIODo not create .frmfiles for temporary tables.UNION ALLworks without usage of a temporary table.Scalability fixes for Power8.Performance improvements on simple queries.Performance Schema tables no longer use .frm files.xid cache scalability was significantly improved. 
        Replication
          
            Optimistic mode of in-order parallel replicationdomain_idbased replication filtersEnhanced semisync replication: Wait for at least one slave to acknowledge transaction before committing.Triggers can now be run on the slave for row-based events.Dump Thread Enhancements: Makes multiple slave setups faster by allowing concurrent reading of binary log.Throughput improvements in parallel replication.RESET_MASTERis extended withTO. 
        Optimizer
          
            ANALYZEstatement provides output for how many rows were actually read, etc.EXPLAIN FORMAT=JSONORDER BYoptimization is improved.MAX_STATEMENT_TIMEcan be used to automatically abort long running queries. 
        Security
          
            Password validation plugin API.Simple password check password validation plugin.Cracklib_password_check password validation plugin.Table, Tablespace and Log at-rest encryption (TDE)SET DEFAULT ROLENew columns for the INFORMATION_SCHEMA.APPLICABLE_ROLEStable. 
        Galera Cluster plugin becomes standard in MariaDB.Wsrep information in INFORMATION_SCHEMA: WSREP_MEMBERSHIPandWSREP_STATUSConsistent support for IF EXISTSandIF NOT EXISTSandOR REPLACEfor:CREATE DATABASE, CREATE FUNCTION UDF, CREATE ROLE, CREATE SERVER, CREATE USER, CREATE VIEW, DROP ROLE, DROP USER, CREATE EVENT, DROP EVENT, CREATE INDEX, DROP INDEX, CREATE TRIGGER, DROP TRIGGERInformation Schema plugins can now support SHOWandFLUSHstatements.GET_LOCK()now supports microseconds in the timeout.The number of rows affected by a slow UPDATEorDELETEis now recorded in the slow query log.Anonymous Compound Statents blocks are supported.SQL standards-compliant behavior when dealing with Primary Keys with Nullable Columns.Automatic discovery of PERFORMANCE_SCHEMAtables.INFORMATION_SCHEMA.SYSTEM_VARIABLES, enforce_storage_engine, default-tmp-storage-engine, mysql56-temporal-format, Slave_skipped_errors, silent-startupNew status variables to show the number of grants on different object.Set variables per statement: SET STATEMENTSupport for Spatial Reference systems for the GIS data.More functions from the OGC standard added: ST_Boundary, ST_ConvexHull, ST_IsRing, ST_PointOnSurface, ST_RelateGIS INFORMATION_SCHEMAtables:GEOMETRY_COLUMNS,SPATIAL_REF_SYS | 
  
    | MySQL 8.0 (link) | MariaDB 10.2 (link) | 
  
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        InnoDB
          
            InnoDB Version 8.0AUTO_INCREMENTvalues are persisted across server restarts.Index corruption and in-memory corruption detection written persistently to the transaction log.InnoDB Memcached plugin supports multiple get operations.Deadlock detection can be disabled and leads to a lock timeout to increase performance.Index pages cached in buffer pool are listed in INNODB_CACHED_INDEXES.All InnoDB temporary tables are created in InnoDB shared temporary tablespace. 
        JSON
          
            Inline path operator ->> added.Column path operator -> improved.JSON aggregation functions JSON_ARRAYAGG()andJSON_OBJECTAGG()added. 
        Security
          
            Account management supports roles.Atomicity in User Management DDLs. 
        Transactional data dictionary (DD).Common Table Expressions (CTE, recursive SQL, Series creation)Descending IndexesScaling and Performance of INFORMATION_SCHEMA(1 Mio table problem)Deprecation and remove of features. MySQL 8.0 is currently in a very early stage (DMR) so this list will increase over time! | 
        Security
          
            SHOW CREATE USERCREATE USERandALTER USERextended for limiting resources and TLS/SSL support. 
        Performance
          
            Connection creation speed-up by separate thread. 
        Optimizer
          
            EXPLAIN FORMAT=JSONimproved. 
        Partition
          
            Catchall partition for LISTpartitions. 
        Introduction of Window functions: CUME_DIST, DENSE_RANK, NTILE, PERCENT_RANK, RANK, ROW_NUMBERSHOW CREATE USERstatement and limiting user resource usage introducedCommon Table Expression (CTE) WITHclause for recursive queries.CHECK CONSTRAINTsupport.Support for DEFAULTwith expression.BLOBandTEXTcan now have default values.Virtual computed columns restrictions lifted.Supported decimals in DECIMALincreased from 30 to 38.Temporary tables can be referred to several times in the same query.Multiple triggers for the same event.InnoDB/XtraDB 5.7.14 was merged.ANALYZE TABLEimplemented lock free.CONNECT engine supports JDBC table type.NO PAD collation support.Table cache can auto-partition introduced.New Window functions: LEAD, LAG, NTH_VALUE, FIRST_VALUE, LAST_VALUESlave binary log read throttling, delayed replication, and binary log compression implemented.JSON functions addedOracle style EXECUTE IMMEDIATE.PREPARE STATEMENTunderstand most expressions.TRIGGERSenhanced byFOLLOWS/PRECEDESclauses.I_S.USER_VARIABLESintroduced as plugin.New status information: Com_alter_user, Com_multi, Com_show_create_user.New variables: innodb_tmpdir, read_binlog_speed_limit.DML flashback introduced on instance, database and table level.GeoJSON functions added. 
        To come soon
          
            MariaDB Column store (ex. InfiniDB)MyRocks? MariaDB 10.2 is currently in a early stage (beta release) so this list will increase over time... | 
  
    | MySQL 9.0 | MariaDB 10.3 (link) and 10.4 | 
  
    | No details are known yet. MySQL developer meeting took place in November 2016. | 
        Suggested features
          
            Hidden columnsLong unique constraintsSQL based CREATE AGGREGATE FUNCTIONNew data types: IPv6,UUID, pluggable data-type APIBetter support for CJK (Chinese, Japanese, and Korean) languages. Include the ngram full-text parser and MeCab full-text parser .Improvement of Spider SE.Support for SEQUENCESAdditional PL/SQL parserSupport for INTERSECTSupport for EXCEPT MariaDB 10.3 is  currently in a very early stage so this list will increase over time! | 
Please let me know if I got something wrong or forgot any significant feature for theses 2 MySQL branches.