I've used the 13 inch models for dev since the 2010 models. You really want to actually see these models in person I think, the 11 is tempting because it's the same power but that screen is really very different.
I mean 13 inch MBA is on the refurb store atm in stock so maybe it's a sign to get it. My thing is like I have a 15" MBP so getting the 11" would be a bigger contrast in size as opposed to the 13" if you see where I am coming from.