I would repair it. Fiberglass on the back side and a small amout of filler to smooth it out on the front. sand it leaving it rough where the fiberglass will be applied so it holds well. If there is chunks missing, use tape on the front to give it something to hold the shape. The tape usually pulls off after the resin is dry. then sand it smooth and use a small amout of filler to blend. Clean things good after any sanding with Laquer thinner or a pre paint prep cleaner.
I repaired all of mine and they turned out nice. My front lower spoiler was crack up pretty bad and I was able to repair it with the same method with good success. I'm not a expert body guy, but its not all that hard.
I try to repair things like this when I can as I am usually not happy with the way repop parts fit.