Our current rig bought in 2007 has a very thin glossy-textured single sheet of fiberglass with seams to the front cap, rear wall panel, and rolled-over seamed to the sides. It has held up well, but as you can see, we store our rig indoors, so anything would hold up well for us.
We owned this true seamless fiberglass rig from 1983 to 2007, made similar to a Coach House. The only issues with the material were cosmetic. It got chalky with age and impossible to keep it looking nice, hence our new rig has the full body paint job for ease of appearance maintenance. It also developed superficial cosmetic stress cracks here and there which were of no concern. We replaced it with our Phoenix Cruiser 2350 because in our later years, we needed a lot more creature comforts than our little Mirage provided.
We would have gotten a Coach House back in 2007 but the following reasons dictated otherwise.
1) The Coach House was too tall for our garage
2) back in 2007, it was double the price of our Phoenix Cruiser
For us in our situation with indoor heated storage and our financial limitations, we made a good compromise. Our PC works exceptionally well for us. Like pnichols and others have mentioned, some features are great in one way, but restricting or problematic in another. It's all about trade-offs.