[chucker]

Really, the only thing is: do you tax your machine a lot, with sustained workloads? Do you compile, render, etc.? If so, a Pro will kick in the fan to avoid throttling. The Air won't; after a few minutes, it will start throttling slightly.

For most users, it doesn't matter, and the Air will provide a better user experience: no fan, virtually no moving parts. An iPad-like don't worry about it device. But for Pros, the Pro is in fact slightly more fitting.