I don't know how SC's sound algorithms compare to other programs. (Maybe someone with firsthand knowledge of this can chime in?) But a very large part of it, however, is the user. Curtis Roads not only knows the nuts and bolts of DSP, but has cultivated a personal aesthetic in which to apply that knowledge. In his hands, arguably any tool could be made to sound good. In tinkering with different languages and systems over the years, however, I'm left with the impression that Csound and SC were (are?) easily top of their lot in quality and expressiveness.
As to whether CDP can rival SC in sounding "good", I feel strongly that the answer is Yes! In transforming sounds, however, the nature of the input has a lot to do with what you get out--CDP won't magically sound great on its own. Above all, it needs the user to apply it sensibly to the particular input sound, or at least recognize a sensible accident when it occurs! ;-) Even processes that, by design, "butcher" the input sound may be exactly what you need to achieve a desired effect. CDP is as good as they come, imho. For proof, listen to some of the transformations Trevor Wishart uses in his recent work.
