I personally prefer Photoshop to Illustrator for most projects simply because the sheer control you have over every single pixel of the image. Certainly Illustrator is a very capable program, but at least for a good deal of what I do, it takes significantly more time and effort to get a similar (same is impossible) result as I would have in Photoshop.
It should be noted that I do not leave vector curves vector, though. After they're finalized I rasterize them.