Seamark is better for me
Seamark is Sunbrella with vinyl heat fused to the underside. The cost difference is minimal but the benefits are superior: never leaks even when touched, looks great, outside can be cleaned with a soft brush without losing waterproofing, the inside can be cleaned with soap and water or any spray like 409 and a sponge to keep mildew in check and it does not get the "Sunbrella Sag" in heavy dew weather. None of these can be done with Sunbrella.Yes, Sunbrella is good, but Seamark technology has surpassed it. Any canvas shop can quote both and the difference should be around $100 or less for a dodger.The majority by far of the sailboats we do at Boat Tailors are now done with Seamark.The related link below explains the properties of Sunbrella, Seamark and another highest quality product - Stamoid.