AGM Zero maintenance. Sealed. Can be mounted anywhere, even inside the RV under a bed or wherever there is space. Can be mounted sideways. Can withstand a much deeper discharge, & recover, than a flooded battery. In storage, without parasite loads, discharges at half the rate of a wet cell. Good for many more discharge cycles than a flooded battery. Has a lifespan 2-3 times that of a flooded battery.
No, AGMs are not cheap however when all of the above is factored in they make sense especially if some dry camping is going to be done.