If you intend to do high latitude sailing, and you choose a
catamaran, you'll be adding a lot of weight to it in
insulation to keep it from raining below decks in near freezing temperatures.
Our boat is a custom built cruising boat, but lacks adequate
insulation to keep the aft cabins dry. We had our first
winter outside the tropics this year, and the moisture below decks from
condensation, from breathing and
cooking, and just air getting below the dew point has been a difficult problem for us, not sastisfactorily addressed.
Ann
PS. If you tell us where you want to go, it will affect (favorably) the input we can give.