I didn't look into that much depth on the issues / feature lists etc.
Regarding whatever Krita is doing, is it embedding the sRGB profile to your file correctly? Perhaps gimp is doing that in the save step. Not sure if PNG can do colour profiles like jpegs and other image types... but that might be the cause.
There's one thing GIMP looks amazing for though, and that's for doing texture mapping and all that sort of stuff. You can do the same stuff in Photoshop, but it isn't as "plainly labelled make normal map" filter / button as what it is in GIMP.
I can't remember off the top of my head and I'm too lazy to open Krita to see what the dialogue box says x_x It was definitely doing (or not doing) something and I haven't done 2d digital art this entire year again and probably should just to test out the new version (I think it's gone up a couple of minor versions since I last used it x_x)
I have a Blender add-on for texture mapping these days ^_^
though I have to try out a new one as the one I have stopped working on the newest Blender and apparently stopped existing too