What is better catamaran or trimaran?

Tri's have a tendency to give you more open deck for the weight. The Cabin Space to Weight ratio is a little worse than cats or mono-hulls in that more structural material is required to maintain three hulls instead of two (or one). Lateral resistance is greater, as is drag, so they're harder to tack, but need less of (or no) keel. Some complex pyhsics come into pay when you calculate hull speed, so I can't answer that one here. Tri's are a more stable but less forgiving platform. If they turtle, they're stable in that position too, and thus very hard to right. Overall, and for these reasons, I personally would go with the cat, and I think most (but surely not all) people would too.