photoshop is a piece of software to edit and manipulate images (which has in some versions the capability of akwardly importing RAW data)
Aperture is a piece of software (like Adobe Lightroom, Bibble, Breeze Browser, Phase One) to organize and "develop/adjust" your Raw files ... basically a RAW converter with a chance to optimise your workflow. So it is aiming at something completely different than Photoshop.
Since I shoot RAW only, all my images are processed through the RAW converter ("developed in the darkroom"), but only few of the resulting JPEGs get serious photoshop-editing afterwards.