I must admit, I had the same "dilemma" when trying to choose the ideal laptop for college.
I've been very attracted to the MBA, especially due to its style and very light weight.
However after doing more research and playing with them both, I ended up ordering MBP.
For me the logic was as follows:
1. The MBA is limited in RAM and HDD, neither of which can be upgraded - and I want to keep my laptop for a least 3 years (until the AppleCare runs out). Also, the MBA's battery can't be swapped on the fly so you have to charge it every few hours - can't go the whole day on campus without recharging it somewhere at some point.
2. You actually lose a lot of screen on the MBA due to the relatively thick bezel around the screen - they could've fit a 14.1" screen in there, although the thinness may have been a limiting factor there. In comparison, the 15.4" screen of the MBP goes much closer to the edges - which gives you a much better screen-size-to-footprint ratio.
3. The laptop I'd choose would have to be my one and only computer, and have to perform lots of functions effectively. Just read the MBA forum for a day and see how many issues MBA owners are having with performance issues, core shutdowns, overheating, etc.
4. Although the MBA is definitely lighter, you'd have to carry around many more accessories with you given its limited ports, lack of CD drive, etc. whereas you can just take the MBP *and an extra battery!* with you for the entire day - no superdrive, USB hub, or even a charger to worry about!
5. This may sound silly but I liked the positioning of my hands on the MBP a lot more than the MBA - and the edges might not be as sharp on the MBA as on a regular MB, but they are still sharp!
6. Last but certainly not least: with the student discount, you get $200 off the MBP whereas you only get $100 off the MBA. If you then add $99 for the superdrive, you end up with the exact same price for a base MBA as for a base MBP. This is where it boggles the mind as to why you'd buy an MBA for college!
Having said all that, my situation is fairly different, as I am a professional having worked (and earned my own dough) for 8+ years and just now finally going back to business school - not starting undergrad.
If I were you OP, I'd seriously take everyone else's advice: save your parents the $2k they'd unnecessarily spend now (or invest the $2k you've saved up yourself, if that's the case) and enjoy your MacBook until you graduate from high school.
When you do, see what's currently available, take advantage of the back-to-school promo, and enjoy the latest dazzling technology!
-Marc