What are you going to want hooked to your TV and why. What system do you think will dominate.
Personaly I think the PS3 will move a head of the 360. The 360 last I checked was most likely NOT going to be backward compatable, had less games to play, sue thier customers more for mods, and had falty power cords that could cause fires.
The PS3 however is backward compatable, will support high def, blue wave DVD, regular DVD, and just might have another Linux dev kit come out for it for $99 like last time.