I agree about the Nacra being the only choice between those two, considering the number of people and the weight you are going to be putting on the boat.

I just want to add that there is nothing "delicate" about the Nacra 6.0. It is a very strong, well-built boat. And, even though you are used to monohulls, you will find the Nacra 6.0 very responsive and very easy to tack.