The factory is surlast which is right on par with sharkskin. Diff mfg use diff names. Sunbrella is def the best. Kind of depends on what you are looking for. If you are just wanting a cover to cover the boat while in a garage or storage area with an occassional use outside or rowing in downpour sharkskin is fine. However if you are looking for a cover to store a boat outside or on a lift sunbrella is def worth the upgrade.
CURRENT: 2008 SANTE 210
2000 Mastercraft Xstar
2004,2005 Ski Centurion Avalanche C4
2003, Ski Centurion Cyclone
99,2000,2001, 2002 Ski Centurion Elite V/Hurricane/lightning
88 2001 Nautique