Urethane or Fiberglass Wing

So I've got the cash burning a hole in my pocket, and I'm ready to buy a body kit. I've pretty much decided I'll be going with the abcExclusive reproduction Saleen kit, for the way reduced price, and also from what I've read, the fitment and quality can't be any worse than OEM Saleen kits, and most people seem satisfied with their product. I plan to buy the kit in urethane (they make a fiberglass kit but I've become wary of fiberglass because of some of the threads I've read). The kit comes with the front and rear fascias, and side skirts, and I plan to buy the matching urethane side scoops. But my question is on the spoiler. I've read that many people have horrible fitment issues with the urethane spoilers, and since it won't be exposed to road hazards like rocks and cars, I'm leaning toward the fiberglass version of the Saleen wing they sell because it seems as though it would have less of those issues common with the urethane spoilers. Opinions? Experiences?

Meh, not so much a fan of the wingless look, I've got my heart set on the Saleen wing anyway.

I have an 04, I planned on purchasing the one as shown in the picture. I've got my mind made up about that, I don't like the other two styles of Saleen spoilers for my year, so there's no convincing me other wise on that. It's that wing, and all I still need to know whether fiberglass is ok for the wing, or if people feel the same about the wing as they do about the ground effects, that it should be urethane. From what I can tell, fiberglass should be easier to install, and sturdier than the urethane, and won't have to worry about it getting damaged by road hazards and whatnot.