if "well-being" is the metric, the nuclear family has no chance compared to the clan-like extended family structure of many Asian or Mediterranean cultures, for example.
I was thinking about this as I walked by the hospital near my apartment. There are generally 3 types of ambulances idling on the side of the building: A generic hospital vehicle, one for Asian people, and one for Jewish people. I'd never seen those ethnic ambulances before moving to Brooklyn. I wonder how much specialized ambulances contribute to well being and health.