I have owned both types (Jayco's) and currently own a aluminum frame trailer ( Jayco). We had no problems with the wood frame Jayco trailers, but I will agree it was harder to keep clean ( black streaks) and wax than the fiberglass with aluminum frame.
We live here in the mid west and with the wood frame trailer( aluminum sides ) I was always concerned about hale damage when bad storms approached where hale was reported. With the aluminum frame trailer I am not as concerned about the hale issue.
For the record if I were to purchase another new trailer I would go with the aluminum frame, fiber glass side.
G Reed.