Kevin,
6 V FLA (Golf Cart) batteries must be vented. They also must remain upright or they will spill corrosive electolyte fluid and they require periodic maintenance to check and top off the electrolyte fluid in the cells.
AGM, Gell and LiFePO4 batteries are sealed and do not require (or even facilitate) electrolyte level checking/topping off. Also while the battery compartment should be vented the amount of gasses vented by these batteries is tiny compared to FLA. Another consideration is orientation, most if not all of these batteries do not have to be upright and will not spill.
An advantage to using 6 V deep cycle batteries is that you can connect two 220 Ah batteries in series to get 12 V and 220 Ah. While each battery weighs about 66 pounds they can be moved around by one person and put in a regular battery box.
In comparison a single 12 v 220 Ah deep cycle battery is twice as large as a single 6 V and weighs about 140 to 165 pounds. Putting one of these beasts into a camper would be no simple task.
A 12 V battery having the same weight as one 6 v 220 Ah battery (around 66 pounds) will only have about 100 Ah - 120 Ah capacity (there is no free lunch with regard to plate size and Ah capacity)
It is however reasonable to look at using a single 100 Ah -120 Ah 12 V LiFePO4. A single 12 V 120 Ah LiFePo4 battery can provide almost the same usable capacity as two 200 Ah 6 V batteries because it can be discharged more deeply than a AGM, FLA or Gel cell battery and it weighs about half as much as an equivalent size (Ah) AGM, FLA or Gell cell. However the cost is significantly higher.
All of these battery types have pros and cons which should be considered and which may make one or another a better choice depending on the particular use situation (on-road vs off road, minimal venting, weight, Depth of Discharge and number of deep discharges over the lifetime, etc).
Regards,
Craig
