I played Unreal Championship, which I loved. I liked how there were different teams, and even a few "leadership" stats if I remember. It really convinced me it was a tournament. I also loved the Lightning Gun, which they got rid of.
I hate UT3 because the "teams" appeared to be thrown in there for the hell of it, and then focused on the "Ronin", who look all look like Marco Fenix from Gears of War.
I also did not like the vehicles. I liked the idea, but the maps that used them always gave you the regular, boring vehicles, and not the badass Necris vehicles, unless BOTH teams had the Necris vehicles.
The maps that used vehicles also sometimes used it as more of a "move faster" mechanic than a method of killing. In one level, Sandstone or something, I remember finding an amazing looking plane, and was eager to use it. When I tried to though, it was far too big to go anywhere but up above the plateaus, where there was invisible walls. Maybe it was just the confusing map, but it appeared the crack in the cliff was where the flag was, and the game wouldn't let me get there via plane.
UT3 was more of a "Gears of War Online" that DIDN'T just focus on heavy use of the Lancer.