I had a wood-framed trailer (corrugated AL siding) from Jayco that was not very sturdy, and required some extensive warranty and driveway repairs to salvage it.
My weekend warrior was also wood-framed, with bonded gel-goat fiberglass. It was very sturdy. In fact, the body seemed stronger than the frame.
My current Ourdoors RV (AF/Nash sister company) is Aluminum-framed with bonded fiberglass. The body seems the stiffest. Nothing ever works loose, there's no sawdust working its way out from behind fiberglass. It does form condensation at the studs where the WW did not. ORV/Northwood use fir inside the structural aluminum frame, which makes it structurally better and probably helps a little with the insulating.
I still don't trust the weld/joint methods used by most of the big RV makers in their aluminum frames. But I won't own another Aluminum-sided trailer because its dents and punctures too easy when you drag it through the forest.