With a 12v system we have found that starting is instantaneous, whereas
when we used 6v the engine would sometimes have to be turned over for
a long period even though it was tuned correctly. I know some people who have used a 12v system for years with no problems, after all a Jimmy
is not likely to be used on a daily basis. I realise that a Jeep may be used
for daily transport and the 6v system is adequate for starting but the
downside is the lighting, glow- worms come to mind.