trailers: fiberglass vs. metal

What is the conventional wisdom on fiberglass top trailers? I've never had
any experience with one. Should I keep it this way and stay away from it by
all means? Or is it OK, really, and not much worse than Al top? How long do
they last and how much maintenance require? What are the pros and cons of
each? I'd think that metal is more durable and virtually maintenance free,
while glass may be a bit lighter. Anything else? Thanks! -- Y