Tube output stage CD player ?

The output stage on a DAC / CD player is similar to a phono stage for a cartridge. So a tube cd player uses tube(s) to amplify the signal to line level.

Which one sounds better?

That one has been and will continue to be debated on this site forever with respect to amplifiers, preamps and the like. Were you to ask the designer of a tubed unit, doubtless he would say the tubed one; likewise, the designers of the Levinson and similar players would say solid state. And while I prefer my tubed dac, I'd be the last one to assert that an Ah! Tjoob CD player sounds remotely as good as an Accuphase. Ultimately the one that sounds "better" is the one you think sounds better after careful listening, I guess.

A cd output in a tube player can sometimes be advantageous. If you do not have any other glassware in your system, it is one way to go about getting the sound of tubes(albeit not the preferred way). Or if your system sounds a bit harsh, tubes can smooth things out. I generally believe that if you are a certified tubeophile(which means you are already in possession of tubes), a tube CD player is unecessary(but that doesn't mean you can't go in that direction). I think it was a better idea in the older days of digital. When the sound was overly analytical, dry, and sterile. Newer players are not like that as much. Which one is better? Depends on you, your system, and your room.

Hey Trelja, did you ever own one of the early Analogic Designs players made by Scott Nixon (later called Anodyne)? I did, and for the very reasons you mentioned about early digital. Gave it to a musician friend years ago, and I believe she's still happily listening to it (although I wonder how the tubes are holding up).