I have the 13" Air and my Brother and best friend both have the 15" Retina. You cannot go wrong with either one. Depends on how heavy of video/gaming stuff that needs to be done.
Doing regular video editing and photoshop and stuff the Air is more than efficient. My friend was editing 4 HD video clips on the fly off of his Thunderbolt HD... that I would not be able to do with my Air.
For a college student I would probably recommend the Air unless he is planning on doing a lot of gaming or going into an engineering program where something memory intensive like CAD will need to be used.
2007 Z4 3.0si Coupe • 6 MT • Black Saphire Metallic • PP • SP • Heated M Seats • Clutch Stop • Stubby
2008 R6 • Raven Black • GPR Steering Stabilizer • Comp Werks FE • Hotbodies Flush Mount Blinkers
2008 Nissan Titan XE King Cab Long Bed • 4x4 • Line-X