My opinion- I like steel because I like to work with it. I have used fibo for a while and think it is harder to repair (more labor intensive) but still fun!! Fibo is, of course lighter, and I think has a smoother, glossier,' plastic' appearance when painted- not to say you can't get a GREAT glossy paint job on steel- I think it is all personal preference. You want to race go for least weight. I'd rather have steel in front of me when (or if!!) I ever get into a fender bender.... or in the case of fibo- fender breaker!!! Good Luck!!
++Doesn't come "prepped" to mount on your vehicle. Often times you will have to drill holes in order to mount.
++Sometimes doesn't align correctly because of molding imperfections, requiring you to remove bracing and cut the fiber-panel and re-glass it to make it fit "Just Right"
++Doesn't rust obviously
++Big learning curve in working with sheetmetal. But it's tons of fun. I'm learning as I move forward...my truck probably won't be finished for 10 years, and chances are it's not going to be an award winning show-truck, but I'm LEARNING and that's the best part.
I ran glass fenders on my 36 PU for 20 years and 207,000 miles. Dinged a rear when I had a minor jack knife towing a car, Did not even make me whimper , quick and easy repair. I'm now redoing the truck and am putting new glass fenders back on cause I loved the first ones. I do lay roofing tar on the underside to eliminate the crows feet cracks from tire slung rocks. Fiberglass fenders never rattle or squeak!!!!