POR is probably more durable in the long run and if you spend time lying on your back marvelling at the beauty of the bottom of your rig then it may be worth it.
ZR is available in rattle can, qts and gallons in various colors and will not kill you if you breathe it in as POR will. ZR is also less expensive, easier to apply, easier to get off your skin and does the job it is intended for.
