You are really overthinking the whole thing IMO. It doesn't matter what the materials are as long as they are put together right. Some of the best reputation RV's in the industry are stick built. I own a cheapo Keystone Hornet (stick built w/aluminum siding) that is 9.5 years old and never had a bit of trouble with it. Don't get hung up on materials as they all will fail if not properly constructed. Pay more attention to individual units and the care used in putting it together. In the end no matter what it is made of it will come down to build quality and proper maintenance.
