Thats only in Unreal 3, look at the rest, it gets a good lead as resolutions get higher.
Also the cards out performs in games with AA on, thats where it really shines
Plus if DX 10.1 is a 20% increase in fps with AA enabled, its should be interesting.
EDIT: A game that supports DX10.1 could come out over night, (patches etc) remember assassin's creed?
Either way, in the long run CrossX seems to be at an advantage. (assuming you have the board that support it).