I'm going to start this thread by quoting good ol' K1BOS from another thread:

I had two Dstar radios and finally got rid of the last one. My least favorite digital mode. Audio so bad that it sounds like nails on a chalkboard with tones of digital break up.

John, I wonder what radios you were using? I now have both an ID-51A and ID-5100A and I find the audio quality to be quite good, and I get reports on both (but primarily the 5100A) that my audio sounds excellent. I've heard a few comments that the latest generation of Icom radios sound improved over previous versions. That said I see a number of people using ID-880H's which also sound good. To me even the various dongles, DV4Mini, etc. sound good, and I have to wonder if it's just improvements with the newer models. I know you have an ear for audio given your background.

I've not heard Fusion yet, but of the modes I have heard I agree that P25 sounds the "richest" in quality. I think DMR sounds pretty decent as well. I guess it comes down to individual preference.

My local DMR repeater is still not back on DMR-MARC but I have definitely been enjoying DStar; never thought I would but I'm pleasantly surprised.