Either computer would fit your needs, it's really up to how much you want to spend and what you want. The 13" Air is a little more portable than the 13" retina, although probably not enough for it to be a deciding factor. I expect the MBA to run a little faster than what you currently have, but probably not noticeably unless you're doing anything graphically intensive. I'd say go to an Apple store and have a look and see what you like best.