I am really eager to hear the feedback from someone who has used and sharpened an HH !
I have an HD & my HH lands today.
I will sharpen, compare & provide some feedback soonest.
You might as well add your ZDP-189 to the comparison too.
Ok, I have just finished sharpening the 150mm HH Kono with a 12 degree relief and 17 degree micro bevel finished with the Jnat Ozuku Asagi spritzed with 1µ Mono diamond spray.
It was a total breeze.
IMHO (not scientific testing and all that, just my perception based on feedback & sound from the stones - Chosera lineup), I am of the opinion that the HD is slightly harder to grind....???
Both appeared to reach much 'o much the same level of sharpness.
....but that might be because my HD is a 240mm gyuto....????
Would be nice to hear from others doing similar....
Bring the ZDP-189 into the equation....you kidding me, ZDP-189 is way harder than the HD & HH combined - also I reckon it takes a better edge.