Should I buy a 13 MacBook Pro or a 13 MacBook Air?

The MacBook Pro has more upgradeable items like the hard drive and Ram that you can replace yourself and the MacAir has the Ram and hard drive (flash drive, SSD, etc) soldered directly to the main board so you can't up grade them later.

The MacBook Pro is a bit more powerful then the Air but the Air is much slimmer and lighter then the MB Pro.