I've flown both, but most have been the single clue, never the less, I really don't have a preference.
OK465, I think that when we got N27 it had the dual clue FD installed and the Kingair 200 that was stolen from us had a dual clue as well. That was changed to a single clue on N27 when the cockpit was overhauled and all that telephone wiring that the FAA had installed for test projects was removed.
Basically I think that one is most comfortable with what one is used to, if military you are more likely to prefer the dual clue and if civilian, you prefer the single clue.