I went with Flagship based on Z-Spar's own statement about its much higer UV protection. So far, so good, but I haven't used anything else, and I only have 2-3 months on it so far. If UV is better, what's the down side compared to Captain's?

Also, how likely is a varnish/epoxy incompatibility? I was't willing to trial & error, anxious to get on the water, and not interested in testing, so I went with one of a few recommended by Pygmy (for the System Three they supply). I had a can of Interlux 90 a marine store assured me would be ok for System Three. It actually looked good in a test patch, seemed to bond ok, but I just couldn't face a major failure potential, and went with the recommendation from PYgmy.