Unfortunately you're kind of comparing apples to oranges. Aperture, in my mind, is more of a photo management program than a photo editing program. Sure, it has the ability to edit photos, but it's nowhere near as capable as Photoshop is. Conversely, Photoshop is the standard by which all other photo editing software is measured, but its photo management is non-existent which is why Lightroom exists.
If you're serious about photography, then you may want to consider Aperture+Photoshop or Lightroom+Photoshop. If you're just looking to do rudimentary editing, then you can most likely get away with using Aperture alone. If you couldn't care less about photo management, then Photoshop alone is your answer.
Ask 10 photographer's what they use and you'll get 12 answers. So, good luck.