Yes they are all good points and each one is correct in its own way. The fiver we are negotiating with the dealer at this time does have 3 inch walls with more insulation than I have seen. The under belly is enclosed and heated and the roof is pvc not rubber. It has an inverter for the residual frig and the leveling system is all automatic with jt strong arms stabilizers.
I am still sorting it over in my mind but I am starting to lean toward the fiver. We generally stay in one spot for weeks at the time. Once my DW retires permanently we are going cross country again but this time take as many months as we like. We will never full time as we love our s&b.