Tim,
Very few hulls are built from pre-preg Marstrom hulls are the exception.. The rest are usually wet layup so the UV protecion has to go on the outerside as there is no UV protection in wet layup Resin.

The protection of choice for hulls is usually gelcoat becuase of its durability.

With wet layup a competent laminator will get around a 50/50 resin fabric mix by weight. The pre preg has the resin impregnated into the fabric in a lab and is controlled to a choice of 37 or 39% of resin.
When you are looking at laying up a mast pre preg delivers UV protection, a much stronger layup due to the stronger resin matrix and it will be lighter becuase of the carefully controlled improved resin/fabric ratio.

As far as hull construction goes it is mostly wet layup. I think Nacra claimed the Infusion is the first cat built with resin infusion.
The Blade F16 by VM was built using resin infusion for nearly a year now and there is another manufacturer that I know of using resin infusion for hull production.

It is certainly my view that all production boats should go to resin infusion as this produces a better product using a cleaner process. Maybe this will be what is needed to bring the weight of main stream production hulls down as the process itself pushes quality up.

Just the way I see it.