[TonitrusEN]

There are up sides and down sides to both fiberglass an urethane..

The upside on fiberglass is that its light and if cracked, you patch it, paint over it your fine, downside is that it will tear if stress is applied.

urethane upside: more durable will not tear or crack easily. but if you dent it, and bend it back, and try to paint on it, you will have spider web cracks all over the paint the first time anything touches the bumper.. just my experience..