I gotta say, if I didn't already have a 360 and shitload of XBL friends, I would consider getting a high powered PC, hook it up to my living room TV, buy a 360-PC controller and Steam the crap out of some games. Steam has had hella great prices lately.
see, if it weren't for the fact that most of my friends are on xbl, and I already have a 360, I'd be sorely tempted to forgo the 360, since most of the exclusives are also on PC, minus things like Halo.
As for my vote, I went for Sony.