Like Pest said, the net code is much better, I've been on 64 player servers with no problem, MOHAA starts to choke at about 40 players for me.

It also seems to me that the gameplay is suited for BOTH run-and-gun and sit-back-and-aim styles of play. It's really nice when I can grab an SMG and charge in like a madman, or sit back with a rifle, pull up my sights and pop krauts one by one. Both are equally challenging in their own way in COD. MOHAA stock was almost exclusively run and gun (mostly with shotgun), realism was almost exclusively campers and MG whores.