I have a Surface Pro (128GB) with a bunch of development tools installed on it, and I use an MB Air for development too. I will take the Air over the Surface any day of the week. With the Air I get: better keyboard, better battery life, snappier response, better screen, more storage, more RAM, and for some reason the Surface is "unbalanced" and feels like a brick when you pick it up. The Surface is less convenient to use, you cannot prop it up on your lap, you cannot prop it up on your stomach and lay in bed. One other distinct note in the Air's favour, and this is a huge personal preference, it isn't running Windows 8.