Readers Digest Condensed version.
If you mainly pedestal camp with full hookups, a 12V battery with your existing charge controller would be in your best interests.
If you mainly dry camp, off the grid, a pair of 6V batteries would serve you better, along with proper recharging equipment to get them near fully charged, which will take a charger capable of delivering 14.8V in bulk charging mode, for best results DRY CAMPING. Your stock charge controller may or may not be capable of this, in particular if it is a WFCO or Progressive Dynamics model.
Battery charging maintenance is a whole another subject you'd need to do a search on here.