The Macbook Air 13" has a higher Resolution than the Macbook Pro 13" Plenty of Processing power in both machines, the Flash Memory in the MBA makes up for the slower clock speed over the MBP.
I noticed you are hoping to use them for a little gaming e.g WoW now the MBA would be awful lack of GPU power and also heat issues. Since my 13" Macbook Pro can run WoW perfect but the heat is an issue after a few minute the fans ramp up to 6200 RPM (Max i believe) and the temps are in high 80's (CPU Temp) now this cannot be healthy over a period of time surely. This is since the GPU in the 13" model is embedded into the CPU, now if you were looking at the 15" with Student discount if possible would be a better route to go down as it has a separate GPU and would deal with heat and have more gaming ability.
As for the screen the size is ultra portable and I find it great day to day. Prefer to use this than my 27" iMac although the iMac is handy to leave on 12 hours a day without ruining the battery etc.
Edit.. The OS took a while to get used too only minor shortcuts etc, but great piece of software all user friendly no maintenance needs, very low risk of viruses i believe. I would never go back to Windows. Worth the pledge, maybe check the Mac area on this forum, check discussions, pictures and so on.