As an alternative to this, I offer a reason to choose MySQL over MariaDB based on pure speculation: MariaDB has merged with SkySQL, who is a VC funded company.
Being funded by VCs is not a bad thing in and of itself, but since most VC funded companies seek an exit strategy, it makes the stewardship of MariaDB at risk of being purchased by the next Sun or Oracle. In an ideal world (ideal for the future of MariaDB, that is), SkySQL would want to be acquired by Google or Facebook, but those two companies have thrown their lot in with MySQL by way of WebScaleSQL.
I mean, say what you will about Oracle, they've put out some pretty good releases of MySQL, they've done some things I don't approve of but right now they seem pretty committed to improving the product. A lot of the stuff in this thread is speculation about what Oracle COULD do to MySQL, rather than anything they HAVE done.
Being funded by VCs is not a bad thing in and of itself, but since most VC funded companies seek an exit strategy, it makes the stewardship of MariaDB at risk of being purchased by the next Sun or Oracle. In an ideal world (ideal for the future of MariaDB, that is), SkySQL would want to be acquired by Google or Facebook, but those two companies have thrown their lot in with MySQL by way of WebScaleSQL.
Disclaimer, I work for Percona.