there is no real disadvantage for one or othere one big thing keep in mind is a 12v alternator output about 14.6v and a 12 dc generator output is 12v at X RPMS you would whant a generator that has an output os about 13V at your idle but will not exseed much more then 17V at any rpms that you will mantane for a long peread of time (keep inmand that it is the rpms of the pully not your engine)
