The Naniwa 12K is a great finishing hone as already stated. After that, you can strop on leather untreated with abrasives and then shave. However, I recommend you put "something" between the 12K and the untreated leather strop.
After the 12K, I use 0.25 micron diamond on felt most of the time. At times, I use 0.3 micron chromium oxide on balsa.
Then, to the untreated leather strop.
How does the .3 chromium oxide on balsa stack up against the .25 diamond on felt?
I don't think it makes much difference whether you use 0.5 micron chromium oxide or 0.3 micron chromium oxide (Kremer Pigments) or 0.25 micron diamond, or you name it in that grit range. In fact, going from 12K to untreated with abrasives leather works. If you don't use an abrasive of some type, you just have to strop a little longer to tame and sharpen it to shave readiness.
But, that doesn't answer your question below...
The diamond cuts faster than chromium oxide. That is the primary difference. Some believe chromium oxide produces a milder smoother bevel and edge than diamond. I can't detect any difference in the final edge, so use diamond simply to save time. (But, admittedly, it doesn't save a huge amount of time.)
Also, diamond is less messy, easier to use than chromium oxide.
Naniwa 12000 is a very fine finisher. A step above what most people use even. Some of us are just... well...
You know the guys who wax the walls of their tires?
One of the maybe most well regarded honemeisters of all, Martin @ Rasurpur finishes all his razors with the 10K & then just strop on Kanayama linen/leather.
That settles it, I need a Naniwa 10K!
Good to see you're back from the land of SE!!
I'm still there often, but Swedish framebacks made me come back. It's like they were made for Coticule edges!
The 10,000 grit stone is for a very high polish of the edge. The quality is like a sword polishing hone. You can nearly shave with a razor which has been honed on this stone. (Just try a good stropping with the Cordovan hanging strop without any paste and you will be amazed.)
I am using the 10K in the end for all razors and I do not use any paste after that; just the cordovan strops.