On a good pow day, Copper's Spaulding bowl is a hoot. There are some mammoth cornices (like Cornice Chute) and the run-out to the Resolution lift (the Cross Cut run) can be a high-speed blast. I've had a great time in the Spaulding Glades as well, but the trees are fairly tight.
The Sierra lift that serves the Sierra Bowl (which faces N) and Copper Bowl (facing S) usually opens late on pow days due to avi control but once it opens you have access to some really great, if not super long, terrain.
They run a (free!) snow-cat out of the bottom of Copper Bowl that gets you part way up Tucker Mountain for some really, really good steeps and glades. Prepare for a healthy 1hr hike though.
Oh, and don't pass up heading far west (to Far West and the Union Meadows); if there's even 4-5" of new pow it can be a ton of fun, although the run-out to Timberline can be a bore unless you want to work on drills or are goofing off with the kids).
I grew up in Vail; I remember entering the bowls before anyone else with my Dad who was in ski patrol. Nothing compares to Vail's back bowls.
And now with China Bowl and Blue Sky Basin...
But Copper has great terrain.