I owned a Late 2011 13" MacBook Pro and now have a Mid 2012 13" MacBook Air. Here are my thoughts:
-Screens: The color on the Air is a little more washed out, but not something I would notice unless I put the two next to each other. The Pro had an excellent screen, but the resolution was terrible and the black bezel made it harder to see in certain light. It also showed more finger prints, which annoys the crap out of me.
-Speed: As far as speed goes, the Air is much, much quicker thanks to the SSD. It takes 15 seconds to launch to the OS X desktop from a cold boot, whereas the Pro was 30-45 seconds. Again, this is because of the Air's SSD.
-Processors: I did a decent amount of video editing on the Pro and it was very quick. Honestly it was more power than I needed, but it's always to good to have more than less. I haven't done any editing on the Air, but it's damn quick too. Looking at the benchmarks, they are about neck and neck with each other.
-Weight: My friend has a 13" Pro and I was installing ML on it for her the other day and who knew that a Pro could feel heavy? I never had complaints with it before but compared to the 13" Air, the difference was noticeable.
If you're looking for a power desk warrior, take the 13" Pro and upgrade to 8GB of RAM and a fast SSD w/ external HD. If you want to be more portable, the only choice is the 13" Air.