There shouldn't be much of a difference between regular MySQL and MariaDB. FWIW I'm using MariaDB for my own site, b/c I despise Oracle. I wouldn't recommend using Google or AWS DB backends, unless you're comfortable with getting vendor-locked-in (which nobody in their right mind should be). With all of that said, in general you should pick the DB you're most familiar with, as that reduces the risk of misconfigurations.
