So, which is the best finisher and why do you think so.

I read that you are not suppost to use a thuri on a razor after you have used a coti. Why?

I have a nani 12K Now. How will both of these compare?

I heard that a coti puts a smoother edge than other finishers. Why?

I know that is a lot of questions. I know everything you hear or read isn't necessarily so. I want to draw from the collective experience here.