I know there are a lot of posters (myself included) who say that the brush sets are not as good quality as the regular brushes.

I guess I've been assuming it's true, but I have no "hard" information to back this up.

If someone has "inside", verified information and could settle this argument once and for all, that would be greatly appreciated!

By hard information, I don't mean comments like "doesn't feel as nice (on your skin or in your hand)" or any other type of subjective, personal observations since those vary greatly, I mean real info: do they use the same materials? the same manufacturing process? quality control? ... that kind of stuff.