Are both of these computers un-upgradeable after the initial specifications are selected? I'm considering buying a MBA,13, base model, and only upgrading the ram. I'm trying to compare this computer to the base model 13" Retina MBP. I understand the difference in screen, but I'm more concerned with performance. How do they compare? Surprisingly, Google doesn't yield a whole lot of comparisons. For real world use, no major video processing, is the upgraded processor going to show any kind of difference? Also, with all of the Macbooks getting rid of the ethernet port, is anyone else concerned about the speed or wireless internet vs wired? I was always under the impression that wired was much faster. Finally, I'm upgrading from a 2010 MBA with 4 gb/ram, 1.86 ghz intel core 2. Am I going to notice a nice speed bump, no matter which computer I end up with?