Avoriaz
The best base in the Portes du Soleil, high, car free and right on the circuit.
Avoriaz tops the list because it solves the area's main weakness, snow reliability, by sitting high above the rest, and it does so as a completely car free village with terrain straight from the door. Children can move around safely and the whole circuit is immediately accessible.
It edges out Morzine on snow security and convenience, since you are already on the mountain rather than riding up to it. The bold modern architecture is not for everyone, but for snow, position and a safe car free base it is the clear pick.