Hello DK and SK,

. We are glad to have you join us here and we look forward to reading of your adventures and experiences. I am sure you will enjoy the website and forums. Good luck, stay safe and keep us posted.
An aluminum skinned unit is usually constructed of wood frame and some batten fiberglass insulation in the wall. A Filon or fiberglass unit is usually constructed of aluminum framing, Styrofoam block insulation that the entire wall and roof sections are vacuum bonded. Which ever you consider be sure that no water has ever entered the roof or walls as this can cause much damage that is very expensive to repair.
Take your time and first understand how you will use the coach. Lay on the bed, stand in the shower, sit on the throne to see if the unit(s) under consideration "fit".
Enjoy the hunt!
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Mike, Certified Master RV Technician
Amy, RV Merchandiser; Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser w/ Banks & 2 toads