Gutter connected reduces the exposed surface area - thus less costly to heat on per square foot basis. Fiberglass - still used although not as popular as ten to fifteen years ago. FRP is more resistant to breakage and puncture or vandals. Etching and dust abrasion - darkens over time. Easier to cool an FRP house.
Construction is a lot easier than glass.
FRP used to be a terrific fire hazard - not any more. Acrylic and polycarbonate - ten years or so in use. Institutional settings, gable ends, becoming more popular. Future is in moveable benches. Cost of benches should not be overlooked.