I have both the Nani 12k and the Shapton 16k, which by the way are basically equal in grit size, and tend to use the Shapton more than the Nani. The reason is I seem to get better feedback and repeatable results from the Shapton than from the Nani. The 12K and 8K Nani also seem to have an issue of creating little black dots on the surface during usage that normally I wouldn't worry about, except these black dots seem to cause the blade to skip during the stroke, and re-surfacing is required to stop it. I try to eliminate both 8K and the 12K Nani because of this issue. As a final note, I sometimes use my Spyderco UF as a final polishing stone, for an incredibly smooth and polished surface, before using paste and then stropping.
Ray