Looking to get a MacBook. Not sure if I should go with the Air or Retina Pro. This will be primarily a work computer with a large amount of data loading and word processing, web browsing. Also, may do some personal photography work (but I have an iMac already). And will be traveling with it. If I were to get the Air, I would upgrade to the 8 GB of RAM and then thought maybe I should be getting the 13" rPro which has a faster processor and the additional RAM. But after further reading it looks like the I/O speeds are actually faster on the Air? I'm not sure what would be best for my needs, if the Air will suffice or if the Pro is actually significantly faster? I'm fine w/the display and don't have a need for the Retina display. I'm more concerned w/the portability and performance.