I find that the display size also affects the case size. At 6'3", anything smaller than a 15" is no longer a "laptop" because it falls between my legs. The case sizes have actually gotten smaller and lighter. This is one of the many reasons I'm disappointed with my 13" MBA, other than build quality. It is so light that you have to be careful or it could tumble as the ratio between the weight of the bottom to the weight of the top has decreased greatly. When I had the 13" MacBook it seemed to workout in terms of portability but I now wish that I had gotten the 15" MBP. I think that the new 15" MBPs probably travel as easily as my old MacBook. Needless to say my vote was for the 15" screen. I have the iPad for everything else.