Short answer: it depends.
IMHO, most DVD players sound worse than CD. It is my understanding that DVD players are trying to do too much -- all the picture decoding stuff _and_ the audio. And then, depending on the design, if they're using the same path, CD playing suffers as well.
However, a nice, fast external DAC can make it sound awesome. I, Robot
on Classic Records
DAD sounds simply unbeatable. That is my setup (sometimes -- right now, the DAC and DVD player are in different rooms).
But that's only on the few that have a 24/96 PCM track, and those are far and few in between.
That said, I think combo SACD players might be different, since they are perfectly adequate for playing CD's.
But if you already have it, why are you asking? Why don't you tell us yourself?