My vote is for black
It is cheaper, you have more chances to get it right and I think it looks better.
I thought about going with white (same stuff you are looking at) but it would have taken too long to get for my timeframe. I don't really think the boat stuff is significantly better quality.
One question, how are you planning to get the plastic to stay tight to the contours near the sides at the back where the flat section meets the curve? I couldn't think of an easy way to make shrink plastic work with that design (hence, my current cap doesn't taper in at the sides).