In a real hailstorm that would damage aluminum to the point it would leak, it would also damage fiberglass to the point it will leak. If fiberglass is hit with hail that dents aluminum, it will also damage the fiberglass shell, but it takes a while before the damage makes itself known, sometimes it will start to crack and open up as moisture enters, and other times, nothing happens, but heavy enough hail will spiderweb the fiberglass, you just don't see it. My Coleman got nailed in a heavy hailstorm that cracked the windshield of my truck, and has plenty of tiny marks all over the front, but has not leaked at all, they are just cosmetic.
The aluminum and fiberglass trailers make for a larger lighter trailer than can be done in a stick and tin, but some stick and tin can be lighter in weight than a similar floorplan fiberglass one. My 274BH has over 3K pounds of cargo capacity and GVWR is 7600. I saw a similar floorplan in glass that had the same GVWR but 1000 pounds lower CC.
Both will leak eventually, and the fiberglass one, once they get wet and start to delaminate, they are done, stick and tin, you can seal up the leak, replace the interior that got damaged and keep on camping.
