they each have classes & BF got it right.
If TF2 was BF I'd be really disappointed, BF has way more watered out classes than TF should have, the cool thing about TF is how each class is so different, and basically only good for one thing. the heavy is useless for running, the scout useless for defence and so on. In BF there are classes, but like most so called class-based games, you can almost ignore your class and do everything with any class..
I'm not saying thats a bad thing, or that it doesnt fit into a realistic setting, but its not TF.