I've never used or hear D-star, but that's interesting.
I've heard P25 and NexEdge side by side, and Nexedge is as good, if not a bit better than P25, in my own opinion. To add to that, I can get a Kenwood NX-410 NexEdge 800MHz radio for about $600 with battery and charger, etc. A comparable P25 radio would quite a bit more.
One of the nice things about the Kenwood NexEdge radios is that they can be flashed to do P25. It uses the identical vocoder, just different format.