I was there for those shows and Jon can scream with the best of them. He does seem to have stopped lately though and I'm not sure why. Most people would say he's "saving" his voice I guess. However I have just seen 3 live Bruce shows where he screams his head off - and puts on 3 hour and 15 minute shows - and does it on back to back nights. Bruce is also about 12 years older than Jon. Obviously different people have different voice issues but I think Jon could hit the "raw" button a bit more. He used to do it so well.