There are essentially three types of trailer structure construction and everything in-between.
1 wood walls with sheet metal screwed to it.
2 luan/fiberglass sandwich
3 Metal tubing cage or frame.
Each has its plusses and minus. Each category is more expensive then the preceding usually. As builders sort of do things in-between there is some middle.
I recommend looking at the Cedar Creek construction video. Their #3 system is shown in detail.
Also brochures tend to have exploded views of their units that show the construction.
As a guy with a structural background I chose #3.
#1 is easiest to repair.
#2 often has delamination issues. All the structural strength is dependent on that.
I am not that knowledgeable.
The point is do your research. Know what you want and what you are getting. In a previous post I listed what mattered to me. It is a long list. Food for thought.
With so many possibilities the knowledge of most sales persons is suspect at best. For sure what he sells is the best in his mind. Or he is a poor salesman.
Let the buyer beware. The sales person is not your friend.