The 12 V set up uses a Zener Diode, much simpler wiring
The 6 V set up switches the alternator coils, and the switch has an Emergency setting for starting with a flat battery
, this has a lot more wiring to the switch. it does not really regulate, just changes output to max with the lights on, its not great and will boil a battery
if a lamp bulb fails since the lamps loads are needed to balance the demand/ output.