For photo editing, I would go for as much resolution as possible. I use the 15" Macbook Pro with Retina, with 2880x1800 and that makes it usable. I would prefer a 17" but that is not available. My wife has the 13" Retina version, but I find that too small.
The higher resolution screen gives 4,7 mega pixels (full screen) resolution, which is more than 2 times the other. in my view that is worth to paying a little extra for.
1DXII, 5DIV, 5DSR, 8-15/4L, 11-24/4L, 16-35/2.8L III, 24-70/28L II, 70-200/2.8L IS II, 100-400/4.5-5.6L IS II, 200-400/4L IS 1.4x, 17/3.5L TS-E, 24/4L TS-E, 35/1.4L II, 100/2.8L IS Macro, 300/2.8L IS II, 600/4L IS II, Zeiss: 15/2.8, 35/1.4, 55/1.4 Otus, 85/1.4 Otus, Profoto B1