Simply put, I've skied most of the top 10 listed and to be honest Mammoth is so much better than any Aspen Mt. it's not even close. Sure Ajax is longer top to bottom but there's nothing there like the top of Mammoth. Jackson is great but talk about a nightmare to get to, and if you're not a quad black dimond skier, good luck. There's no other place like Mammoth, 20 ft of snow can fall in 3 days, then you can be skiing in deep powder on blue ski days that you think someone painted. Simple drive from LA, or any place in Southern Cal and I'd drive right through Tahoe any day to get to Mammoth. The drive along 395 in either direction, from LA or Reno is unreal in beauty. Come spring time you get all the desert bloom, then unreal skiing. And the icing on the cake? The last 2 seasons I've skiied on my birthday which is the 1st day of summer, and on the 4th of July, and the conditions were amazing. Then you come off the hill and hang out at the many lakes and or boat down the road at Crowley, or just take a 2 hour drive through Tioga pass to Yosemite. So if you're looking not only for great skiing, cause the mountain will challenge every level of ability without boring you, you also get the adventure off the hill as well. No other resort offers so much to do in nature on and off the hill. If you ever get the chance, ski it in summer when you can do all the other things around the area as well, take 5 days and do something different everyday and ski each day as well. Oh, as for night life and things to do in town, it's ok, but you'll run out of things to do there in a hurry. Not a Aspen social scene, but wilderness like no other.
Pros: A mountain for every level, snow almost year round, wonderful people, easy to get to.
Cons: Weekend crowds, bad storms if you get caught in one. Limited night life.