Epoxy resin has become a very popular choice for surfboard construction in the last 10 years. Polyester resin has been the standard in surfboards for 50 years. Epoxy is 5X stronger, has better flex properties, better UV resistance and very low VOCs (and no smell when glassing) than Polyester resin. Polyester resin is is brittle and yellows much faster than epoxy. The only advantages of polyester are its curing times are faster than epoxy and it sands to a shinier surface.