It depends on your level of skiing/boarding. Seymour doesn't have a lot of advanced terrain but it does have a great park.
Grouse has a bit of everything. Cypress has a bit of everything too. I'd recommend Seymour if you're beginner-intermediate, otherwise one of the other two. It also depends on the snow. When we were there the Vancouver mountains snow wasn't the greatest.
We did a day at Whistler, left two hours before opening and then left at 4 to come back to Van for a hockey game. It was a long day, but oh so beautiful. Whistler definitely has the wow factor, but then so does skiing overlooking Vancouver on a clear day or night.