Answer by
LeheckaG (1826)
Fiberglass garage door's advantages:
inexpensive, lightweight, better resistance to coastal salt-air corrosion, potential-translucency, can be molded to look like wood.
However, fiberglass garage doors can discolor/yellow with age, break/crack more easily, and do not have the insulating capabilities of polyurethane insulation sandwiched in-between steel sheets.