Hard to say what my preference is but I've skied the following mountains in my life (besides the NY mtns)
Stowe, VT
Jay Peak, VT
Sugarbush, VT
Mad River, VT
Killington, VT
Okemo, VT
Mount Snow , VT
I have to say, of VT I'm partial to Okemo. Not sure why I just like it. They're all great in their own way though.
Breckenridge, CO
Arapaho Basin, CO
Keystone, CO
Loveland, CO
Copper, CO
Vail, CO
Steamboat Springs, CO
Winter Park, CO
Eldora, CO
Of all the mountains I've ever skied, the best days skiing were Steamboat 1, ABasin 2, Vail 3, Breck and Keystone. The first day at Steamboat was NYE Day '94 and we had something like 30" of fresh snow and not a cloud in the sky. It was glorious. Bumps were as big as Volkswagen beetles and covered with the freshest powder I've ever seen in my life. We had 2 days of that.
I lived out there for a few years. In fact, I ski bummed one winter in Breck. Never made it to Butte or Telluride other than the Bluegrass Fest. Had a free ticket to Aspen and never used it.
My 14 year old son has been begging to go out West since he could board. I figure for his senior year I'll take him West as a graduation gift. But I have my eye on Utah. A week of Snowbird, Alta, Park City would be fun. And who knows, If I can hit the lottery by then I'll hit those three and then make the 8 hour drive over to Squaw Valley & Heavenly for a couple of days. Bucket list stuff.