Coming off a tangent in the Belleayre gondola thread, I figured this would be a good discussion for a separate thread.
To me, things that make a mountain "ski big" are many lift sections or starting points, long runs, and a low density trail layout.
Whiteface has only slightly more skiable acreage than Windham, but anyone who's skied them both would say that Whiteface skis way bigger. It's all about the layout here. After taking the Facelift up, there's another lift that you have to go up to reach the summit. There are three separate mountains and two of them are over 4000 feet. The runs are much longer and more challenging at Whiteface.
Belleayre has three different starting points, but the runs are rather short and the trails are very closely spaced, making the place ski small. Mountain Creek has less acreage and vertical, but skis bigger due to the time it takes to traverse across the whole mountain, and the relative separation of the four peaks.