Not to be argumentative or anything, but My 6v Generator charges at idle. Granted, it charges MUCH better when running at higher RPMs...
One of the main reasons that someone would want to have a 12v Generator is to keep it looking original. The only people who would know any different would be people like us who can tell by looking at it what voltage it is.
If you don't care, go for the alternator, if for no other reason than for expandability's sake.
