The transfer is the product
Every other 'best family destination' list starts with terrain parks and kids' clubs. Fine. Those exist here too. What doesn't exist elsewhere is a hub airport 30 minutes from 500-inch snow. That is how you ski on the day you land. That is how grandparents can fly in for three days without a puddle-jumper.
You can match the mountain to the kid
Beginner: Brighton or Solitude. Luxury first-timer: Deer Valley. Town and mixed ages: Park City. Teen who can ski: Alta or Snowbird. Same rental car. Same week. Colorado can do a version of this in Summit County; it cannot do it without I-70 and 9,600-foot bases.
The honest downsides
Canyons close. Inversions look apocalyptic from downtown. Alta will not take your snowboard. Park City on Christmas week is a mistake. None of that undoes the airport.