You don't want to start playing on XBL anyways, download mame and play that if you haven't started already. You'll find a lot of "jobbers" on XBL, the community there sucks really bad. If you have a good computer, with a decent internet connection, I suggest playing on mame. You'll get a better gaming experience and you'll be playing the actual arcade port of the game. UMK3 on xbox has been edited, so there are minor changes in the gameplay, that actually really do make both versions of the game feel pretty different.
[COLOR=Hot Pink]Keep going with this and you will be banned. Last warning.[/COLOR]