PS3... That said, I don't feel as strongly that way as I did two years ago.
BC is a must or I would just say 360 for the lower price. In addition to BC, some reasons include Ratchet, MGS4, LBP, Blu-Ray.
Back to real life... there is about as good of a chance as me getting both a 360 and PS3 as there is of me obtaining neither, or only one... I really have little desire for a 360 or PS3, and I am content with the Wii. If I do pick one or both of them up, it will probably be as a low-cost bundle from ebay.