Id say PS3. I AM biased seeing as how ive never really liked the 360 much but I dont think my bias goes far enough to skew what I would recommend to people.
Even if you don't care about platform exclusives in general, id still say PS3 as you dont have to pay for online and get a blu-ray player to top it off.
360 definitely has better online interface and structure still, even if the margin is thinning.