Whether it be Iris Pro GPU or the discrete GPU. Or will I notice lag, beachballs, etc? I have the 13 rMBP right now and it lags even when I use a thunderbolt Apple Cinema Display. Trying to decide if I can get away with buying a 15 rMBP again, rather than making the switch to a Mac Pro, which isn't that portable. To be clear, I don't play games, I sit and write code all day, read, have lots of browser windows open, etc. The 8GB rMBP I have now is always overtasked. I wish I had gotten more ram. I don't remember the 15 rMBP being that bad, but I could have amnesia. You can see my other thread, with lots more detail here: http://forums.macrumors.com/showthread.php?t=1840773 Thanks!