It depends on the day. On a powder day, you can't go wrong with John Paul Express (to the right of Needles Gondola). Nearly all the terrain at the top is black or double black, so there's never a line there. There's some trees and glades, so if it's foggy, you still have some visibility (unlike Strawberry). At the top of John Paul, you can access the Tram up to the top of Mount Ogden, from there you have a variety of options--I'd recommend taking the traverse all the way out to No Name (about a 10 minute hike). This area is beautiful on a powder day and opens up a ton of terrain that is less frequented. If No Name is closed, and the trails next to the Tram are fog-covered, I'd avoid the Tram as visibility will be an issue.
I love Strawberry for groomers. This area is on the opposite side of the resort (skier's right) and is serviced by its own gondola. There are some excellent blue/black groomers and also some great ungroomed blacks/double blacks here. I avoid it on foggy/stormy days because visibility is terrible.
I try to avoid the center of the mountain (Needles Gondola) because this tends to be the most crowded and least interesting. Needles can get really crowded on weekends and it's just not worth the wait.