My other half uses Sunbrella extensively in her business, mainly because of the durability and the fact that they stand behind their product.
There's one alternative that I wouldn't normally recommend, but I'll throw it out there as a way to save money ....
If you google sunbrella and click on the links to various distributors, you'll see that some mention 'first run', usually in small print. Fabric manufacturers/mills such as Sunbrella use a different grade of fabric to set up their machines; This fabric is likely to have a lower thread count and not be of the same quality as their main product. When they're done with the setups, the 'first run' fabrics are wholesaled off.
Most resellers of first run fabrics will sell them at much less than the regular Sunbrella, but there are resellers out there that charge 'almost' full price. So, be sure to read the small print on these folks' web sites.