I just bit the bullet on an MBA myself. I would have preferred to be able to wait until the Pros get Haswell, but I can't really wait any longer due to the decrepitude of my current laptop. If OP can wait, though, the Pro might satisfy him/her.

+1 for awesome use of "decrepitude"

How well do the macbooks run Ubuntu? Last time I looked into it, there were still some issues with the 2013 macbook air running the latest Ubuntu 13.10

Macbook Air. Macbook Pro if you can spend a little more.

Also take into consideration portability between these two. I use a MBP for my main machine - It's a beast, but if you're lugging it around it could get heavy (Although, I could find much heavier laptops). If you want something you will have zero issues with carrying around - The air would be a good choice.

MBP with retina display, you mean? Otherwise you're dropping in resolution.