What West Virginia Skier said regarding 7Springs. The only PA resorts I've skied in Eastern Pa is Blue Mtn, Elk and Jack Frost. Elk is by far the best of those three, I recall that it has some pretty varied terrain with some nice fall line bump runs. When I was there they had just begun to clear some under brush and mark trees to be cut for some new trails the following year. We stayed in those trees for the most part. That was about ten years ago. I don't recall anything really steep or many official glades.
In Western PA, Blue Knob has the best expert terrain, perhaps the best in the state. Extrovert would be a black diamond at any resort I've skied in VT, CO and even UT, Alta/Bird. It is steep, double fall line, two intersecting trails, has snow making and never groomed. The East Wall Glades runs on the same face, all natural so all of the humps and dips that erosion and time created is still there. The Ditch Glade is a huge natural half pipe coverd with trees, it really is a stream bed. Stembogen twists and turns like the old trail that it is and the top part is never groomed. Shortway is a very narrow natural cover bump run, I could go on. There are many more expert glades and intermediate glades as well as long cruisers too. Some on-hill lodging and the ski lodge is lacking, dank and dark but hey, we go to ski and I brown bag and eat in my car. Oh yeah, 1000+ vertical.
Laurel (my home), not open this year and perhaps never more, has the next best expert terrain. There is only 70 acres total with only 30 under the gun. Wildcat is as steep as Extrovert but 2/3rds of it is groomed with the skiers right bumped up and groomed only when it becomes unskiable. There are a number of unofficial glades, one that utilizes the entire 900 ft vertical. The Lodge is small but relatively new and offers great views. Both Blue Knob and Laurel's lodge are at the top of the hill. No on-hill lodging, some private rentals near by.
Seven Springs is the state's largest resort, most acreage, among the nations largest snow making coverage, great lodges, good food, plenty to do off-hill too. There is nothing real steep but there are a few dedicated bump runs with good pitch. Tons of beds from hotel to cabin to condo.
So how do you define best? Me, I love Laurel and it will be a sad day if we don't re-open.