I decided to see if I could improve on my dmt sharpness. The good news, I did. The bad news, I did. It’s not a tremendous amount, and not enough to make me go back to waterstones (yet), but I will leave my hard Arkansas on the bench from now on.
This is my normal sharpening routine.
1. Hollow grind
2. Hit the edge (do it more and more by hand) on the 3 micron DMT
3. Strop the back
4. Hit the 3 micron DMT again.
So here is with just the 3 micron dmt. Back flatten to the DMT well
EDIT: This first picture is what I started with. It hasn’t been flatten yet (at least not by me) 
Polishing the back on the felt wheel with green compound and sharpening with the hard Arkansas stone ( I saw a slight difference from the dmt to the Arkansas) 
Same sequence…. 
I did this with 4 different hand planes. The 2 shown, the Stanley #18, The Sargent 710, and a Bedrock 604 and a Stanley 60 1/2.
All showed a subtle difference. The biggest difference was with the polishing of the back. Sharpening the bevel was barely distinguishable but I could see a slight difference in the resistance.
If, from the dmt, you polished the back with the felt, then sharpened with the dmt, the difference would be almost unnoticeable from sharpening with the Arkansas. I’d have to do it a few more times to really know for sure, but my gut tells me the Arkansas would have a slight edge.