Again, it comes down to what you (advanced or not) like.
I like trees, so I put a premium on those above all other 'advanced terrain' features and thus, some notable 'advanced mountains', while I love them are not my favorites (Those being alta-snowbird and Taos, I love both those places but they favor the expert who loves steeps and chutes, -haven't been to Mammoth but I suspect it's the same.)
For me, I've enjoyed Heavenly and Steamboat more than other resorts for their trees (I also like bumps-so Heavenly is again high on my list).
And even at big expert mountains, I've found I like slightly different stuff than most 'experts' go for-While I love the steeps of the Snowbird Tram -I think I've had my best times at the 'bird skiing off the GAD 2 chair (those steep, chute-like bump runs near the chair are just wonderful-great place to spend a warm afternoon.
At Jackson Hole-I loved the trees on the Moran face more than any other area of that truly great mountain (and the most expert of expert mountains IMHO).
Heck, last year during my trip to Utah-I had my best day at Solitude (yep, solitude)-those tree covered chutes and runs along the near Honeycomb canyon ridge and off the powderhorn chair are exactly the sort of terrain I enjoy skiing the most (and we had great snow and sun that day!).
I guess what I'm saying is that once you skied enough to attain some level of expert (or we'll just say 'good skier'-expert is elusive) ability-you've also become discerning in your tastes and preferences and some places will cater to those very specific personal attributes more than others.
Rule of thumb-Pick places with lots of varied terrain, multiple exposures and good snow-easier said than done-and, I think it should be said that a true expert can make a great day out of just about any mountain (within reason, of course