Help buying my first MacBook

A couple of days ago I decided to buy a MacBook. I started searching and I'm having trouble deciding which one is the best for me. I like games a lot, like call of duty, portal, etc... I don't know if a core-duo macbook will run these games perfectly, so I'm also considerating buying the 15'' macbook pro. I'd also like a macbook with a relative big screen. I'm in doubt about buying these 3 macbooks:

-MacBook Air 13''

-Macbook Pro 13''

-MacBook Pro 15''

Which one is the fastest? Does the quad-core 15'' run games better than the other two? I would appreciate a good answer.

Thanks.

You should have no trouble with the occasional older game such as the original portal it will run fine on the 13" pro. The 15" does have better graphics which should make it run games better, If a bigger screen is also a must have it makes the price difference between a 13 and 15 easier to swallow. The top model 15 should run almost any game released in the last couple years. It probably wont run BF3 or MW3 at max. I think it will run any game that is currently out in a Mac version.

You will want the 15" screen

And I would always get the fastest processor and most memory I can afford. The processor you must choose when you place your order, the memory you may add yourself later.