You suppose that the only measure of efficiency is keybindings. It is not. For me, other aspects of the editor, such as frames, superior auto-completion, and superior compilation mode, make me more efficient. I don't use an editor solely to "edit text." I'm using to to accomplish a bigger objective, such as creating or fixing a program. Overall, Emacs is better at that, and the fact that I can give it bindings that mimic those in Vim also helps.