Oracle, MySQL, & MaxDB also run under OS X.
What you choose really depends on what you're trying to accomplish, as well as your current skill set with DBs and the level of easiness you want in the product compared to its power and capability. How often you'll use it and the number of projects also is a factor.
Filemaker is nice if you're going to be making stand alone DBs and want cross-platform capability. That version isn't cheap though.