There are too many factors upstream to be able to make a sweeping generalization about whether USB or TOSLINK or coax sounds better. USB and TOSLINK from one of our Minis playing off a hard drive via Amarra sounded great and slightly different. I would have a hard time putting one ahead of the other. TOSLINK from a blu ray player playing a CD sounded slightly worse than either. That correlates with my general findings of disc playback vs hard drive playback and also my findings of Amarra vs. CD player playback firmware, so it could have nothing to do with the inputs of the DAC. Coax from the blu ray player was worse than TOSLINK from the blu ray player. Who knows why, could be a cable issue, impedance mismatch or something else.
What I can say is that all three DAC inputs are very responsive to the sources, no problems handshaking. In fact the DAC helped us find that the TOSLINK output of one of our Minis was not working properly.
I can also say that the new digital filter seems to have cleaned up the sound from a temporal standpoint. Transients are cleaner and more dynamic and the decay of notes seems to follow the recording more closely, revealing more of the harmonic structure of instruments and really locking in the image.
