I've run with Dvorak for a number of years now (probably ~4). I have also used vim for all of the standard reasons you have to use vim like things (less, config edits that have their own editors (visudo, etc.), etc.). Emacs was actually the first Unix program that I learned (I'm a native to the Apple world) and I currently picked it back up after being castigated by Yegge's ramblings about how ridiculously awesome it is.
From a strictly keyboard layout stance, I would say that Emacs is probably the winner here because no remapping is required. Other than swapping the Caps-Lock key for a Control key (which should really be done period, the Caps-Lock key is like every keyboard's high-school hickey), I would say that every keybinding is more comfortable to use with Dvorak than with Qwerty. I especially find the constantly used C-x and M-x bindings to be very comfortable to type.
However, vim is really no big deal. 'j' and 'k' are still right next to each other. 'h' and 'l' are at least conveniently on one hand and are on and above the home row. Other than that, it's simply about remapping the keys in your mind for doing things in the editor that you want to hae happen. I personally don't see any reason to remap anything, and I'm high risk for RSI (hence the switch to Dvorak). For keyboard centric apps like vim and emacs, the fact that I can use them comfortably unaltered should be fairly impressive. :)
Good luck!