I find the Norton stones to be...different in the feedback category. As you say, Naniwa seems to keep a similar feel through the line up. Norton stones start off feeling quite aggressive/gritty at the 1K and get smoother as you work up the line. The 4k single grit is noticeably more gritty than the 8k, even if it doesnt have a porous manufacturing defect found in some 4k stones.I like that, but I can see where folks might prefer a similar feedback through the range like Naniwa provides.

I know they rate them by JIS, or at least they say they do. I suspect that is based on the hone's performance rather than it's cutting material particulate size. They don't auto slurry or wear as much as Naniwa stones seem to, I suspect that like a Spyderco Ceramic hone or a Swaty barber hone the harder binder in a Norton hone allows them to use coarser material for a finer polish.

On one hand, I want to get another 8K to compare to. On the other, I don't want (another) stone that's just going to sit around collecting dust. I rarely use my synthetic stones as-is. Maybe one of these days I'll spot a well worn Naniwa, King, or Shapton 8k for sale cheap that I can pick up for testing purposes.