Comparison of the new macbook air and iMac Core Duo 2 2.66
The 2010 11 inch Air is so much faster than a Core 2 Duo - top of the line, 15 inch MacBook pro that it's really not much of a comparison between the newer 2013 Air and anything that isn't a pro based logic board (the 27 inch iMacs tend to be the highest of end "mobile" processors with logic boards that tend towards the pro range).

Unless you need a larger display, I see no reason to shift your entire workload to any of the three last Air machines if you don't wait undue minutes for builds in Xcode to complete. From where I sit, the SSD drives and the 2013 processor lineup make for extremely productive workstations in the Air form factor.