Not sure how important a built-in DVD/CD drive is to you, but the Macbook Air does not have one....
However, it is much lighter and more portable than the Pro.
I love my MacBook Air, and have purchased an external DVD/CD Drive that I can attach to it when I need to upload or download something from a DVD/CD. But, I don't need one with me all the time....
I would suggest that you go into an Apple Store next time you have a chance, and test drive both of them before you make a decision. They are both GREAT machines (my husband has the Pro, and we both love our Macs).
Hope you find what you are looking for!