Mentioning the CCA for your 5er batteries instead of their AH rating might indicate that the OP is not aware of starting vs deep-cycle batteries for use in an RV as the "house" batteries.
Many or most RVs use a "marine/RV" battery that says deep cycle on it but it is really more of a modified starting battery. Better than a real starting battery though.
Not liking those 6s at that store is one thing, but you still ought to have deep cycle batteries of some sort. You can get 12v deep cycle like the Trojan T-1275 but they are expensive. 6s are fairly cheap under $100 each many places.
I don't personally (rightly or wrongly) care about longer warranties. I figure if the thing is no good it will quit soon after first use. Not a factor in finding the best deal (most AH per dollar) in the first place.