Can someone explain to me the practical differences between a product like Varathane spar urethane and say, Z-Spar Varnish?
In my experience Varathane is easier and more forgiving to use and costs half as much as a product like Z-Spar. Is Z-Spar really that much better? Longer lasting? More durable?

Thanks.

http://www.rustoleum.com/product-catalog/consumer-brands/varathane/crystal-clear-spar-urethane

http://www.westmarine.com/buy/z-spar--2015-flagship-varnish--P004_128_001_501