I had 27 students use the new DM and the HK tool side by side at a class I taught on Friday (as well as a Hydry and Glided
Prochem tool).
We tried them out on a microfiber loveseat, a nylon sofa with one long cushion, and a three cushion cotton brocade sofa.
Much of it came down to personal preference (as upholstery tools always seem to do), but here were some points that seemed to be observed consistently:
DM Tool: Faster and more comfortable for the "seasoned veteran" (translate: "tired old wrists and elbows"). It did leave the fabric wetter than the DM, but not as wet as the Hydry or Glided Prochem Tool.
HK Tool: While the DM barely wet the back and cushion (tested with blotter paper in cushions), the HK never wet through, even with repeated passes. Cushions or cushion areas cleaned with the HK tool cleaned as well, but dried more quickly, than those cleaned with the other tools. The HK is heavier than the DM tool, and the tool got a bit hot, but not too hot to handle.
Neither tool were as easy to do detail work with than the Hydry or Glided Prochem Tools we used.
People who bought each tool each felt that they bought the better tool.
Our cleaning company still uses an old style DM (to be replaced by either the new DM or HK after further tests) and a Glided Prochem. We also keep a Hydry tool on the truck for detail work.