GIMP, KRITA OR MYPAINT, WHICH IS IT? 
All of them. 
But how!? 
Krita for the sketch and underpainting, MyPaint for shading (because of the awesome and unique shading brush) and Gimp for everything else.
Amazing, I can't imagine using 5 programs for one work
Nice Photoshop quality
Nice Photoshop quality
I would prefer to have all the goodies in only one program, but I got used to this work flow (like other people who use Corel Painter or SAI in combination with Photoshop for example).
I noticed most professionals use a sai/shop combo, for me it's sai/krita