Now that Mac OS X is such a "grown up" OS, you'll find more binaries and packages for it than for other unix based OSes that run on Macs. So it's probably a good idea to stick with Mac OS X and get familiar with it. The Terminal is nice. And if you don't like the GUI, you can log in as ">console" from the login screen and get the good old console filling the screen.
If you need to learn other OSes, my suggestion is picking up a cheap PC, upgrading the RAM and playing around with that. It's a much more supported platform hardware-wise if you intend to do other stuff than importing video and printing photos.