The way I see it the choice is simple. Since the V2.0 360 I've not heard of any big problems like the old ones overheating causing crashes, ring of death, etc. It has plenty of good games out now its been around for a while, and even a few brilliant ones, like Forza 2, Halo 3, Gears of war, The Orange Box, to name a couple. Online play also works quite well which is a bonus.
I am moderately suprised the PS3 is no more expensive than the top 360 though. An extra £50 (360 elite over premium) for a black case and extra 100gb HD doesn't scream value for money.