Actually the Canyons is a smaller resort that Powder Mountain. Maybe it has the most terrain that is 100% lift served, but Powder Mountain is definitely the largest. In fact it's the largest in the US. They beat Vail by something like 100 acres maybe less.
Overall, I think Powder Mountain would be ok for spring conditions. I think Burritos recommendation is probably dead on for what the Rocky Mountain region is being served up. Not much weather of significance is in the forecast until middle of next week at the earliest. So you might luck out towards the end of your trip. So far, storms look week. Washington is the place to go atm.