MacBook Pro: retina resolution display with IPS, faster processor (uses standard mobile Intel processors rather than low-power processors). It comes with a 1280x800 workspace by default, but since it's a retina display you can make the workspace larger without losing too much detail.
The MacBook Air is great for mobility if you need the absolute thinnest and lightest. The MacBook Pro's IPS display is going to have much better viewing angles and the processor speed will be marginally better. If I were purchasing, I would go for the MacBook Pro. It comes with 8GB of RAM by default (I'd have to add $100 for that with the Air), I like IPS displays, and I don't think I'd mind the scaling for a larger workspace (since things like text don't see degradation). The drop in price means that the price difference is $200 (assuming 8GB of RAM in each).