2? I was always a marine because the motion tracker made the game so immersive. Also you can associate with that character more easily, and it just makes the game really enjoyable, unless you use the smart gun -.- I sometimes played predator just because I liked the films and because of the ability to truly stalk... plus the secondary attack of the spear is win.
I didn't play AvP 2 online. I just played mission. Also have played the expansion. Predator is good if you want to blow some steam but there is nothing like alien that eats heads.
The online play was intense. The predator players were insane they would just hide in some little corner and wait. Then randomly one shot you with a disk. The aliens always infected the humans, and sometimes if they got lucky predators. Man i miss that game. Also, the single player was so intense. I loved the human and alien campaigns.