We use both in our production and staging environment. I've been using both for the last 3 years (5 years for MySql). My opinion at this time is that in 80% of cases MySQL is easier to setup, use and manage.
The problem I see is that simple use cases gradually become slightly-less-simple use cases. And the pain of switching is 1000x the pain of taking a few extra steps up front and using a better database.