If you don't do a lot of camping without hookups than most any pair of batteries would work. For camping without shorepower a pair of true 6 volt deep-cycle batteries is a good way to go as they can handle the deep draw down and recharge process better than starting or marine/rv hybrid batteries.
We usually purchase all of our vehicle batteries from Sams or Costco including our current set of 6 volt GC2 batteries. We primarily camp off the grid and realize that it's how a battery is maintained, and more importantly how it is recharged, than the brand label affixed on the side. Our Interstate batteries lasted 8 years.