Switching is beneficial for the same reasons that car manufacturers switched in the fifties. First, power is amps times volts. Doubling the volts halfs the amps for the same power. This means that wiring is lighter OR on the other hand, more power is delivered at the same amperage.

If you need late model accessories like a stereo, air solenoids, gps, etc, it is tough to find the new stuff in six volts......and the hokey volt a drop resistors arent a good solution.

If you keep it original, six it is....if you modernize, 12 is the way to go. Soon, cars will run on a 42 volt system for the same reason.....triple the voltage delivers much more power thru the same size wire OR you can drop the wire size.