Hi
I'm a professional Graphic Designer.
How can you compare Photoshop with Illustrator, one is a bitmap program the other is a vector program.
If want to change or fix photos use photoshop, but don't design with it. if you enlarge your design it will pixelate thats what vector software is for.
If you want to Design Graphics, logos, business cards, etc use a vector program.
If you want to compare the two, you should ask Photoshop or Photopaint,
Illustrator or CorelDRAW.