I always think hardware sounds fatter because you just route it straight into your mixer or speakers from the back of the box.... no reliance on flakey drivers/is the sample normalised/have i decent soundcard/is my app/souncard it at the right level. Your VSTi will only sounds as good as your soundcard/PC config allows for the most part.

This doesnt hold true for people with perfect setups i agree... just an opinion.