FWIW I had a Unidisc 2.1 and DV-50 in my system for a few weeks.
The DV-50 has much better bass, while the unidisc is somewhat more musical, more of that Linn sound. I personaly like that sound, but had to agree with the wife the DV-50 just was more 'complete' and accurate. I think the Unidisc sounded better on DVD's, and the picture was slightly sharper IMO, but now that Teac is offering the DVI output for the DV-50 (well, soon.. I suspect the video will be a wash).
While I liked the Unidisc, I kept the DV-50. One thing to realize is this player takes a long time to burn in, mine took better than a month to really come around, but when it did, it was worth the wait.