Best bang for the buck is a battery bank that best suits your RVing style. If you are a weekend warrior who always has hookups, you don't need any more than what most manufacturers provide. If you are the short tripper, occasionally overnighting in Walmart or odd dry camp night, a couple of GC 6Vs will do. If you are an extended tripper quite happy to be dry camping for a few days with no notice maybe hours away from the nearest Costco & don't want the chore of watering batterys, then investing in a more exotic much longer lasting, much longer service life, zero maintenance battery like an AGM makes sense.