FWIW, I personally avoid concave edges (as in the plain-edge Vapor, and several of the Emersons). It removes one of the main advantages of a plain edge- being able to sharpen it with a flat stone or hone, instead of specialized equipment. They seem to be getting more and more common, apparently just for cosmetics- but, if you can't lay the edge down on a flat surface, you can't sharpen it that way.