The controller, the way the screen starts up, the obvious lie that it only does everything yet you won't care, the exclusives... there are probably dozens of reasons.
Free Step Dodge
Awesmic
Brute
Free online & no red ring of death probably help.
Awesmic
PS3s get yellow lights of death, however. Online's also a bit less stable.
Brute
Well at least in my experience you get the yellow light far less than the red ring on Xbox.
Brute
It's also lighter and quieter and a bunch of other convenient things.