I have played with Matrix's since they came out and shot DM's when I played for XSF, Gridlock, and Trauma. My all-time favorite DM would be a DM6 by far. They were very smooth and quiet. And they were the last DM to not use an eye-pipe. DM7's were pretty much the same gun but with the addition of the eye-pipe. In my experience I have found that the eye-pipe reduced accuracy a bit. My Gridlock DM6's spread pattern was about half the size of my Trauma DM7's spread pattern. I never cared for the DM8 very much, but the DM9 was a very good gun, and IMO shot better than the DM7/8/10/11's. I have 2 DM12's right now and they are amazing guns. So in order, my favorite DM's are as followed:
1) DM6 - Smooth, Quiet, Flat-Shooting, NO eye-pipe
2) DM12 - Smooth and extremely light-weight
3) DM9 - Smooth
As far as PM's go, my favorite there would be a UL'd PM7. These are very similar to DM6's in my opinion, but I still like the feel of a DM6 better.