On the rubber roof, there is true EPDM rubber then there are the synethic types - big difference between them. I have a TT with a rubber roof and our MH has BriteTek, which some (wrongly) confuse with rubber.
EPDM isn't my favorite, we're on our 3rd MH with BriteTek, I'd buy another in a heartbeat.
Also keep in mind just because it says "fiberglass" doesn't mean it's quality material, some is about paper thin. Also keep in mind, like rubber, fiberglass will break down somewhat over time too. I also dabble in older tractors. I recently shipped a cab roof from one of my parts tractors to Louisiana. The roof I had was metal, it was replacing a fiberglass roof that had deteriorated past it's useful life.
Also "rubber" is a lot easier to replace. I did a new roof on our TT a few years ago, I did a buddies 5th Wheel last fall. I can't do a new full fiberglass roof in my garage, that's a factory job.
IMO I'd be more concerned in the roof condition than the material.