1. rMBP 13'' standard option 2. MBA 13'' i7, 256gb, 8gb ram Which is better? I'm considering what to buy between those two options. I think 13'' is not sufficient for the retina disp. Considering portablity, stablity, and battery durations, Which option is better? Ah, Because I'm freshman majoring in civil eng., I use AutoCAD. for AutoCAD, WHICH IS BETTER??????