GIMP is amazing. Photoshop is amazing. I say they're equal, in my honest opinion.
Photoshop just costs $600 more, but also has a hell of a lot of tutorials online, whereas GIMP has not as many (but still has a lot), and is free. And by my experience, GIMP loads faster, too.
As for tutorials, this may not be a factor if you know what every tool is (or at least the frequented ones) in GIMP and their effects... then you could apply a PS tutorial to that, which would knock off another difference between them.
Photoshop also looks a bit better, but who looks at aesthetics when you're trying to make them?