It depends on what is open, like you mentioned....
At The Canyons, if the Snow Canyon lift is still open, that's where the most wide-open terrain is, but it gets cheesed up quickly as Eddie mentioned.
If the Super Condor lift is open, Boa is always fun, as wel as Apex Ridge.
Any of the blue runs off of the Saddleback chair are OK, but can get crowded at times.
Another world, off of the Tombstone chair is usually good for a few turns, and stays fairly shaded.
There is also a lot of blue terrain off of the Daybreak and Dreamscape chairs, but the trails tend to be narrow, and I myself have not had a lot of time to explore that part of the resort, as I spend too much time teaching.
Park City is always good too, as Eddie mentioned.
Let me know if you have any other questions.....