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.
5DIII, 1DX, 8-15/4L, 16-35 f4L IS, 24-70/2.8L II, 70-200/2.8L IS II, 70-300/4-5.6L IS, 200-400/4L IS 1.4x, Zeiss 15/2.8, 17/4L TS-E, Zeiss 21/2.8, 24/3.5L TS-E II, Sigma 35/1.4 Art, Zeiss Otus 55/1.4, 85/1.2L II, 100/2.8L IS Macro, Zeiss 135/2, 600/4L IS II