When I was running Pomf.se I used MySQL but after shutting it down I decided to use SQLite on Uguu.se and go as far to remove most documentation about using MySQL on it. Recently I started running Uguu on MySQL to test out the performance, to my surprise it runs really well after some tuning.
Due to this I will add documentation about it in the Uguu/Pomf docs again (soon TM), using it on a Uguu install is pretty pointless in reality unless it's high traffic so it makes more sense for a Pomf install. I wouldn't recommend switching tho unless you're comfortable using MySQL due to it requiring more things to configure just to get a basic database and connection.
This is where SQLite wins every time, much faster to deploy and easier to manage and doesn't bog down completely when running on a low specced server. However when you have 32GB RAM to spare you gotta allocate it to something, right? :)
I found this great PHP-FPM process calculator which lets you input your RAM values and then spits out recommended PHP-FPM process configuration, great! Combining this with OPCache has been a joy.