ive been to both, tremblant is sick parkwise but powder and weather arent great, its always cold, i went mid april 2 years ago and they had to close the gondola because of wind and cold. On the otherhand, Jay has great trees and powder. I went at christmas and they didnt have their park up, only a small one which wasnt very good. So for you, if you like powder more go to Jay, If you like park more go to Tremblant