I'm most excited about Zero the Assassin, He's like the fusion of Lilith, Mordecai and possibly Brick (His sword attack looks pretty devastating and he seems to be the only class with sniper skills). But I'm even more excited about the Badass point system and shared inventory. I think that should be more than enough incentive to try out all the classes. 

Im kinda leaning towards Prototype 2 myself. I have the same problem, can't decide between 2 games and can only afford 1 right now. The other one for me is "The Witcher 2: Assassins of Kings" which i know is already good but has no benefits for buying it on release day. However Prototype 2 has quite a bit to offer for pre ordering almost equivalent to the CoD Elite service but for free. So ask yourself the same thing i did, "do you really want to be kicking yourself later for missing out on a truck load of free content?" I know day 1 DLC its a pretty evil thing for a game company to do but if it gets people 2 buy the games new then its working like a charm. Anyway my point im making is Ghost Recon and The Witcher 2 will still be the same full game later down line but picking up Prototype 2 later will end up costing you more for those special little benefits that probably should of just been included in the game as a bonus. Sorry for the giant paragraph for a simple question lol its my b-day on the 20th so I put a lot of thought into this to convince myself which was worth it, even asked friends the same thing u did hopefully this helped.