Only related to Big Sky...
I nominate the Black Bear Bar and Grill for apres ski and/or (cheap) dinner. It is near the Hill Condos in the mountain area. If you are looking for sophistication...this is not the place (but hey...this is Montana). My son and I spent a week at the Hill condos late March last year and walked to the bar several nights. A couple of pool tables, some ratty couches, even one of the old M&M gondola cars from days gone by. Food was decent for the offerings (pulled pork, pizza, etc.). I think it would make a great casual gathering place and suspect they may even offer up some food specials if the group went there.
For a more plush environment for a drink or two after skiing, the Jack Creek Bar at the Moonlight Lodge is very nice. If skiing Big Sky you can still get there since two lifts are shared by BS and MLB (Pony and Iron Horse). However, if you are skiing BS but want to hit the MLB bar at day end you would want to park at the Moonlight Lodge since you would be trapped there when the lifts shut down (unless doing the shuttle).
I haven't been to Scissorbills for a few years but used to enjoy their happy hours - so that sounds good as well.
(I should be working on my taxes instead of obessing over my next B.S. trip....)