Sal has mentioned in another thread that Mules will be coming out in CPM-M4, CPM S90V, 9CR18 Mo and ZDP-189. Im a hunter and the most important thing in a knife to me is edge retention. Im not interested in toughness, stain resistance or any other factor. Which of the above steels has the best edge retention? Is there a steel that the Mule might come out in thats better than these? Thanks for the help.