Marine Spar will last the longest in terms of finish, as its used on boats. Potential issues are its thick and not really sand able. We used it on hand rails in homes but only after a couple coats of normal sand able urethane(sanded between coats to achieve a VERY smooth finish), I can tell you the marine spar will look fantastic and be very very durable. I'd suggest using it on some other like wood and develop a technique before committing to it on your grips, which look awesome btw!!!