It takes almost 30 recharge cycles to work in a 6 volt battery. This is more than 2 years for most campers. A 12 volt works right away. Most people that "think" 6v are awesome typically only plug in. This comes from multiple conversations with different people. The reality is that Costco 12C Deep Cycle RV batteries are 115 amps. Put 2 of these together and you have 230 amps. At 50% discharge is 115 amps. A pair of 6 v gives you the same amp hours. However your cost is double. For me? 12 V all the way. 6 volt does not provide any benefit whatsoever, especially for the cost.
Do the research...