PS3, by far.
The only few 'exclusives' on 360 are playable on my PC in a better version, when they don't come to PS3 later as an enhanced version (bioshock and its new challenges, ninja gaiden 2 sigma, tales of vesperia...)
You don't have any competitor to games like MGS4, LBP, Valkyria Chronicles, Team ICO games, Ratchet, Uncharted, Killzone 2 or Demon's Souls on the 360.
Too many game genres missing on 360. It's not even close.







