I like having everything Nintendo on one box, so I don't have to deal with:
-Buy Mario Kart on PlayStation and get the exclusive Wario character.
-Buy Mario Kart on Xbox and get the exclusive Toad character.
-Play it 30 days early on PlayStation.
-Buy it on Xbox and get two days free online.
-Get the exclusive Rainbow Cup. Only on PlayStation.
-250cc. Only on Xbox.
....and so on.