i would personally not have anything fibreglass on my car, moreso on the front, because it just doesn't hold paint aswell as plastic, so in 5-6 months it'll be covered in crack and stonechips, well thats what hapeed to mine anyway, would maybe get a fibre glass spoiler, but thats about as far as i would go.
just my personal choice though.
however, i've never had a problem with plastic pattern replacements., but i've probably just been lucky