I have both the UD 301 & HD Dac 1. They are different animals and are both excellent. The Teac is (perhaps) more transparent, but less refined than the Marantz, which is very smooth & easy to listen to. Build quality of the Marantz is very good indeed. Teac also good, but more industrial.
The head amp on the Marantz, I feel, is superior to the Teac's - tighter bass, perhaps more drive, variable gain settings. But the Marantz is also perhaps more polite than the Teac, which is rawer and abit rougher round the edges (a trait I quite like).
DSD via USB into both is excellent - locks onto both 2.8 & 5.6 without difficulty via A+. Teac has problems with A+ and appears to accept DoP/PCM conversion only. However via the Teac HD Player it plays (extracted) .iso's very well (either in Phillips or Sony formats).
Teac has XLR out if that is important to you (I like it for my power amp). Marantz has a remote (points for that!).
Overall I would say it's hard to go wrong with either unit for head fi: it depends I would have thought on one's ears and gears. I like each, for different reasons. Good thing is they are cheap enough you can keep both.
I have said it before - it is amazing what you can buy for under $800 these days...
I agree wholeheartedly with what 2leftears wrote: