Z-Spar Captain's Varnish seems to be more widely used for kayaks because; its easier to apply, it hardens better when directly applied to epoxy, and its cheaper. Flagship has higher UV protection which doesn't seem to matter if you store the boat out of the sun.

Do use enough thinner to allow tipping out each application area inito the adjacent applied area without the brush dragging. I have used both Captain's and Flagship and thinned them both 20% in So. Cal. warm weather. I only use Captain's now.

See: http://www.greenval.com/FAQvarnishing.html