If you drop a resin cast helmet, it will likely shatter unless it is a heavy casting. Fiberglass is very strong and light weight, but will be more labor to build. If you're going to do alot of trooping and risk dropping it by passing it around to everybody who wants to try it on, then fiberglass may be worth doing, otherwise, resin should be fine. I'm not sure what the price difference would be it you were to buy each type as I'm bulding my own, but I can probably cast four or five helmets in the time it takes to do one in fiberglass.