I don't know about the Sharkskin but I do know the maufacturers of the Sunbrella material. They stand behind it 100% percent whether it is fading, discoloration, or any other fabric error.
I've had both and currently have Sharkskin. Sunbrella is much, much more water repellent and less apt to damage from sun deterioration. Sharkskin is cheaper and lighter weight--I use it as a dust cover since my boat is in a boat house now. Definitely recommend Sunbrella.