Remember, steel fenders are stock, the way the factory built it. If you ever want to sell the car and find a buyer who's into a factory correct car, he'll ignore your car. Also fiberglass, because it's lighter, often implies track use. This may also be a turn-off to a potential buyer, unless they plan on track use for the car. Fiberglass takes finishes differently than steel, so that can be a factor when you get down to the final finishing and painting of the car. Personally, I'd stay with steel unless they were badly rusted and replacements were too costly.