New MBA vs MBP 13" for iOS Developmet
The things that are easy to quantify are screen real estate. If you want more pixels - get a screen with more pixels. The Air fits 15" of normal screen pixels in the 13" package. The 15" MacBook Pro can have a high resolution screen option like the pixel density of the  base model 17" MBP. The 13" MacBook Pro you list has the almost the same pixels as an 11" Air.

Another tradeoff is the Air will have a much faster IO system due to the SSD drive being faster than a spinning HDD. For light crunching of video and still photos, the CPU in the Air performs close enough to the other CPU in the full Pro line as to not be a big drawback for most. 

The SSD speedup is huge for most developers - so that alone seems to trump most people that run Xcode - they really want to optimize for low latency IO and work iteratively. The downside is a smaller drive. 

Compromises abound!

It takes great discipline to optimize code when your development workstation is running with tremendous horsepower. It almost makes sense in a way to choose as underpowered a machine as you can stand to run your code in simulation. You are forced to preview a bit of what the execution of that code will be on lesser powered mobile devices and entry level consumer macs if they are the end users of your development efforts.

I hope these help you compare the tradeoffs and make a great choice. I envy you for having either of these - people have developed code on far less capable machines than even a 4 year old MacBook - so you really have no bad choice and can let he potential payoff of your development efforts guide how much capital you want to invest before you are selling your efforts.