College student. Should I buy a Macbook Pro or Air 13"?

I'm having a hard time figuring out whether to buy a Macbook Air 13" or a Macbook Pro 13". I'm a Psych major in college so no I don't use any crazy software and I dont game at all. I take notes on an Ipad so I don't carry my laptop around all day but I would like something more portable than my 17" PC and I want to be able to use it for years before I get another laptop. I mostly use my laptop now for internet searching, writing papers/school work, photo storage and itunes. Help me please and thanks! 🙂