xtradb vs innodb [closed]
XtraDB is InnoDB with several patches added. The patches themselves stem from Google, Facebook and others. XtraDB is maintained by Percona and the heart of Percona Server.
You may think of Percona as a distributor who collects, coordinates and maintains patches and distributes an enhanced version of the MySQL server.
A feature comparison between stock MySQL and Percona Server can be seen here:
http://www.percona.com/software/percona-server/feature-comparison
The XtraDB engine is also shipped as default InnoDB implementation in MariaDB. MariaDB includes also stock InnoDB as pluggable storage engine, so you can chose.
Benchmarks show that XtraDB scales better on massively parallel architectures and especially XtraDB is much better suited for write-heavy workload. The InnoDB engine in MySQL 5.6 will incorporate many of the features and advantages that have so far been available in XtraDB only.