I finish on the Naniwa 12k.

The edges are significantly sharper & smoother than my 8K + cro ox, but not quite as sharp or smooth as 12K + .5 paste on a leather paddle strop. The paste build ups on my leather paddle strop though, and the small increase in sharpness isn't worth the trouble of periodically cleaning the build-up off the leather - and the build up is a problem since it ends up with ridges instead of being flat and even.

I suspect using webbing with the paste instead or felt & a spray would solve the build-up problem, but the edges off the 12K (using no pressure) are so nice I haven't bothered to order a webbing & felt strop to find out.