i would go for the 360. depending on where you buy, the 360 is generally cheaper than the ps3... but i do like the 360 controller much more than the ps3 controller, it seems to fit better in my hands.
I would also go for the 360 (not just because I have one).
If you have the ability to use it with Xbox Live, than it has a pretty good selection of games available for purchase on the marketplace.