Whichever you don't buy will turn out to be better.
I bought a fiberglass Cobra 26 years ago for my ASW 24 because I didn't want to deal with leaks between aluminum panels. Later Cobras seem to have a layer that prevents UV from penetrating the trailer. And minor encounters with tree branches, etc., are shrugged off as scratches rather than as unsightly dents.
But...the gel coat did deteriorate. Worse, the top cracked, I believe because of flexing from buffeting on the highway, and eventually leaked anyway! Yes, it was repairable (thanks, UH & P3) but an aggravation.
A couple of guys here have gone aluminum recently and that's probably the way I'd lean, but obviously whatever you do will be a compromise.
Chip Bearden