My Botan and Mejiro are those pink layered type stones which are very hard. I think I read that they are more desirable than plain white. Maybe for ascetics?
The Tenjyou is pure white and a dream to make a slurry with. The stone does ware away fast though and I read that the white ones cut a lot slower.
My Koma is hard but gives up the goods with a little effort and the tomo is great for making slurry.
Another problem I have is tape on the spine some times makes the blade stutter on the hone. There is no way around that though.
Just a thought Mainaman, if the jnat adds nothing to the slurry then why not hone on glass?
I have tried a slurry with a DMT plate a few times and the edge was poor .
I did think that the Nakayama added a little to the slurry when using Naguras because the Nakayama does ware down slowly in places which I assumed was from rubbing Naguras on it.
I will also try to round a corner of my nagura and see how it works
Thanks for all your advise ..