The area you can access is certainly larger than Vail. Like Linville says, it depends on how much you are willing to hike for it. There is the old ski area at the top of the pass. Then you can add in Russell, No Name, and Stanley. Probably 600-1500 acres for each one right there. Those peaks were always bc access during the ski area days. The No Name Shoulder is probably under 100 acres. Then there are the Major drainages to the North. Current Creek, 2nd Creek, 1st Creek, and Zero Creek. Around a 1,000 acres in each one of them maybe more. Then throw in Mines, Mt Flora, and Mt Eva and you probably have another 4-5k right there. Much tougher access though.
Probably in the neighborhood of all three ski areas combined terrain wise and more. How much I am not quite sure, but there are a ton of lines I've looked at that I haven't tried as of yet. I have done a good amount of what is available there.
Needless to say there is a lot to do there. I do have my favorites that I repeat frequently just because they are that good.