Personally, at this point in time, I would buy the PS3. I did, a few weeks ago after the price cut. It's a much better value than an Xbox 360, and the only thing I regretted about the PS3 was that I couldn't play Halo 3: ODST. But that's about it. I don't really like any other games besides Halo for the 360. And I can't think of any upcoming ones either :P
Gosh, I think I'm being a fanboy......here:
PS3: No batteries needed for controller, free PSN, built-in WiFi, Bluetooth, PSP friendly
Xbox 360: Xbox LIVE is better than PSN, controller feels better but no built in battery and the battery charging pack costs money, no built in WiFi
I can't mention any games in that list since they're a matter of personal preference.
EDIT: If anyone wants me to go and complete/get more facts for the list, I'd be more than happy to :) Oh and Snakepit, you spelled "Turismo" wrong in "Grand Turismo" :P