Yea if you have an Xbox and not a PS3 then what else you going to do, not play it or buy a PS3 just for this game?
The real hang up people have with this is not just the game it is the debate on weather PS3 is above Xbox, if they can offer different games - even if it is a slight difference. All in all, say everything is equal will you take something that is slightly inferior or the best one, why not choose the best one then even if it is only slightly better - it is still better.