Gimp is a 'simple and easy to use' version of Photoshop. Photoshop is better. It more professional, have more options and is more precise with the images manipulation. I tried both and I use Gimp because is more easy to use. For better image quality and deep manipulation, use Photoshop.
I beg to differ. I've used photoshop for running on 3 years now and I find Gimp 10 times more frustrating. Photoshop is not hard. And to solve a future question for despair. Adobe Illustrator is not a image manipulating software. Its made for graphics.