Theoretically, at least, it is more advantageous to wire them in parallel according to Peukert’s law. In the RVing world having batteries or battery banks wired independently can mitigate the hassle of waking up to no 12 volts due to dead battery, we have not experienced this issue an always paired up our batteries whether 12 volt or 6 volt. No need to go to a pair of 6 volt golf cart batteries if you are seldom off the power grid, wired in parallel your 12 volt jars should give you a couple of days camping with moderate use.