My experience after a year’s use is similar to big_greg’s: the NT-505 with AKM chip is a bit on the warm and polite side.
But more neutral and less polite, more lively, after extended break-in.
Glassy and hard? Well yes, sometimes, I hear some of that in digital recordings generally, but not so much, here. I suspect that, even if the UD-701 sounds better, there would still be a considerable gap up to the analog sound quality, in my system. Maybe I have old-fashioned "tube and vinyl" ears.
What I know, is that the 505 has been a good, trouble-free investment, so far. I have not yet tested the 505 as a preamp, connected direct to my Atma-sphere MA-1 amps, but I know that it works fine, connected to my Einstein The Tube preamp, and also, the Io Eclipse with volume controls (through the Aux input), used as a preamp. I think this translates to "worthiness" - these preamps are very well able to uncover sound problems.
I have not yet had the time to test the headphone output with my favorite phones (Audioquest Nightowl + Nighthawk). Thats actually my one gripe with the 505 - I thought it had balanced headphone output, but no. My mistake. I should have read the small print.