Fiberglassing is a system. Different epoxies, vinylester's and polyester's (resins) with different glass types and weave, kevlar clothes and carbon fibers plus others will give very different results as far as strength is concerned in tension and compression, especially when layered and combined. Poly may work just fine for you but there are differencies. I have a little bit of experience with fiberglass white water canoes and the damage they can take. Used carefully epoxy is a wonderful resin used with fiberglass.