The information in your quote is nonsense. Some people like 12 V better and some don't. The problem areas are in the gauges and heater blower, etc. If you sort them out you will have a good 12V system. Oh, and there seems to be an overwhelming opinion that 6 V starters work fine on 12 V. However, it is also often stated not to turn it over too long at one time on 12V.!!
