Photoshop is the industry standard, Paint Shop Pro isn't. It's pretty much as simple as that.

Photoshop does much more. People say that they can do the same stuff in Paint Shop Pro, but I simply don't believe that's possible. Photoshop is more powerful and it's as simple as that.

I would however suggest you get Photoshop 7 and not Photoshop CS - It's not worth the extra dosh.