I think that the rectifier/regulator is the part that keeps the battery charge between 12-14v, and that doesn't overcharge the battery. The difference must be in the amount of watts that the stator supplies. This is the information that the webpage gives about the stator regulator/rectifier combo:
New Honda Charging Kit: This kit is a Rick's Motorsport Electrics original design; it includes both a stator and a rectifier-regulator. The kit will put out approximately 150 watts and power a 55 watt headlight if the customers rotor has not been compromised.
