I was sitting on a MacBookPro 13 two years with 128 Gigabit SSD and not "seen problems". In principle, the special problems experienced, but sometimes when the code is very much, plus need some info from another window, which you don't want to switch, but I want to see just close, that would not lose the concentration, then Yes, 13 is not enough. In the end I bought a iMac 27` price compare 15. So a matter of choice. If you frequently take it to work and home you write very little, I think 15 is the perfect option. But if you have the opportunity to sit at one place and you can keep your iMac, and it most likely only at home, then it would be better iMac. Well, probably something like that. In General, You can always buy more of 15 its just a screen.