They cannot be compared. Aperture is a system for converting from RAW, storing, cataloguing and making global corrections to your images. It's strengths lie in it's Library system. Think of it like iPhoto for RAW images on steroids. Photoshop is for making global or non-global edits to single images. It does not maintain a library of images. It can't help you find that one image in 10000. They complement each other.