I am NOT a developer or DB guy but a webmaster who has manipulated mysql successfully for several wordpress sites. I know how to use the command line tool and also to run things via phpmyadmin. I know how to perform basic administrative mysql functions and occasionally to make a custom query.
I am setting up a drupal7 site on a VPS where I will already have a wordpress-mysql instance. But it occurred to me that there's nothing really stopping me from installing another db -- postgresql, SQLite, MariaDB. I am less interested in power than ease of use -- but obviously better performance would be welcome. I would probably need some management tool with a web interface. As I said, I wouldn't expect to be doing a lot of DB work; just the routine maintenance and rescue operations that occasionally are necessary.
The site should be a low or medium traffic site with not a lot of writes, but probably a lot of reads. There would probably not be enough traffic to do load balancing or clustering. (It's for a magazine site).
Is there any rule of thumb for which db to choose? Sticking with mysql seems to the obvious and easy solution; I'm just wondering if there's any reason to think differently in 2013.