The actual waxed canvas ones last and are worth the expense because they can be repaired and re-waxed. The polyester ones I have no experience with, if they are tough and uv resistant then they might be an option.I'm wondering how long it would last in our climate. They are kind of expensive, would hate it if I bought one and it started rotting after a few months.
The waxed ones are very heavy as well.
https://www.tractorsupply.com/tsc/product/weathermaster-10-oz-canvas-tarp-20-ft-x-20-ft
https://www.tractorsupply.com/tsc/search/canvas tarp?