Of Course Photoshop! It looks more professional like and more features than most of them. Photoshop is still the most awesome photo editor ever! Fu*k Gimp losers.
PhotoShop ofc, it's much better to edit things in and you can make nicer things with it. But Gimp is a very nice free alternative and you can also make very nice things such as Counter-Strike sprays and things like that. But i would prefer Photoshop
It's obviously Photoshop. It costs hundreds of dollars, while GIMP is free. If you just want to do graphic editing as a small hobby, then go with GIMP. If you want to take it more seriously, then get Photoshop. Photoshop has more features, and Adobe (The creator of it) is very popular and well known for their excellent products.
Photoshop as it poses more of a professional background. When people hire graphic designers I'm pretty sure the employer would want someone with a Photoshop background rather than a GIMP one.