I think some people simply like the feel of one over the other. Myself, shoulder problems make the hard cams a real bear. The first 6 or 8 inches of the draw are the most difficult for my shoulder. If I get it back that far, the rest is easy. Thus, soft cams are preferred by me. I also like a good valley and the hard cams, seem to have less of one.

I've heard every cam on the market being described as "smooth". From the way the word is used on archery forums, "smooth" apparently is a word used to describe any cam you like. Too me, "smooth" means a cam that gradually peaks and gradually falls into a valley. Anything else is less "smooth". Soft cams are smoother.