I've been skiing mostly at The Remarks this season, it's pretty sweet. Good park: 3 large jumps, 5 medium jumps, some rails and a baby park. Off-piste is decent too.
Cardrona has a sick park
Coronet Peak isn't very good.
If you want a very good park, go to Cardrona, it's where most pros are currently. Remarks is also good though, especially if you're more of an intermediate park skiier