It really depends on the family. If it's a family of gapers who have never skied, then yeah, you'd be better off at Breck or Deer Valley. But if it's a family of lifelong skiers (exactly the same group Alta is marketed towards), then Alta is a great choice.
I guess a couple of the pros for this group would be great instruction, you would be spending time with your family (not separated), great snow and terrain, etc.
However, if you're looking at a family who has never skied before, the few pros would include good instruction and reliable snow. The cons would include very few activities, not very much beginner terrain, etc., etc.