The only choices people make. The size between the 13 inch air and rMBP are like splitting hairs and should really put them both in the same category (In my opinion rule the 13 inch air out). I can see a very big difference in the size/price of the 11 inch air and the rMBP. The 11 inch air is as portable as you can get in a laptop, and if I was commuting, or constantly using it on my lap that would be the obvious choice. When I look at prices of the 13 inch air, the footprint that is almost as big as the 15 inch rMBP(thanks to a very old looking thick bezel), then it just doesn't fit and or make sense. You can get the same amount of ram, ssd storage in the air, but the chip in the air can't be upgraded to match the rMBP's. For the same amount of money you are getting a smaller footprint, faster full sized CPU, wayyyy better screen, faster thunderbolt ports, .46 extra pounds, hour less battery life (real world testing), faster ssd, and its a little thicker. I know some people will say that the .46 pound difference is a big deal but come on, seriously. 9 Hours vs 12 hours advertised is no where near what people are getting. I owned the 13 inch haswell air and it did get the advertised 12 hours but the problem is that I am getting almost 11 hours out of my rMBP.