Have a simple question here. I've a database with around 1 billion records, a server with 200GB of ram to handle it.
What do you suggest for best performances? Mysql 5, Mysql 6 or MariaDB?
MariaDB 5.3 should give you the best performance:
See http://kb.askmonty.org/en/what-is-mariadb-53 for a list of features.