For the 2012 Macbook Pro 13" should I get the 2.5GHz Dual-core Intel Core i5 or the 2.9GHz Dual Core Intel Core i7?

I am a high school student and I am getting my first Macbook Pro. I am not really sure which 13 inch Macbook Pro model I should get. My budget is kind of tight, but I think that I can afford any one of the models but I dont want to spend any money that I dont have to spend. Usually on a day to day basis, I use the web brower, watch movies that I have downloaded, and write a lot of papers. I also sometimes use Photoshop, and while I do not play a lot of games, I do want to have the option if I decide to later when I go to college. The larger hard drive size on the Core i7 model does not really matter to me because I don't plan using more than 500GB. I will be upgrading the ram to 8GB if I get the Core i5 model and it comes standard on the i7. Also, I need this computer to last me for 3-4 years so I want something that will still seem relatively fast a few years down the road. Lastly, while I would prefer getting the Macbook Pro due to its cheaper price and ability to upgrade the hard drive later, I also am considering the Macbook Air Core i7 model, mainly because of the faster ssd and the higher resolution screen. I dont really use the optical drive, so loosing it would not be a big deal. The same goes with the Firewire port or the Ethernet port. What would you guys suggest I get. A Macbook Pro or a Air and if the Pro, should I get the Core i5 or the i7? Thanks