I have at least three finishers: 16K Shapton on glass, Brown Escher, and my J-Nat (Nakayama Maruichi). I gave my beautiful Coticule away(sob!) In my experience, there is not one finisher for all razors. Each razor will need a certain finisher to produce that ultimate edge for you. The trick is determining which finisher will be best for whatever razor you happen to be honing. Everybody has there favorites and I can't obviously answer your question. I suppose you will get many different answers from many of our honers here.
I use a microscope when honing. - I have experimented with different finishers, and yes, I can see a difference in the edge from razor to razor in regard to which finisher will produce the edge I am looking for. If you are looking for one, I couldn't answer that, but I bet Lynn could. He has used them all. The question would be, "Lynn, we are sending you to a desert island where you can hone all the razors you want for the rest of your life. - but you can only take one finisher with you. and what would that be?
Good Luck,
Steve