I always use mariaDB for my new projects.
both were created by the same guy but mariaDB is the "in case Oracle goes mad" version.
mariaDB is in some cases faster, has some additional features and its development is also faster than mySQl, their stable branch updates quite quickly compared to MySQL
For example, CREATE TABLE IF NOT EXISTS is a sentence i use a lot, but it arrived first to MariaDB and later much later to MySQL
Another example of MariaDB vs MySQL is Galera...
it is a master to master server replication, it means you can have 2 servers each with an instance of mariaDB both being redundant and having the same information. and you can do this with... like 5 steps.