I have it on good authority(Cole Dickson) that accuracy is more important than power on the break shot. If you are trying to put so much power into the shot that you need your bridge hand to hold the cue on line, you are out of control. That being said, you should not need chalk on your break tip either. The only time I chalk my break cue is when I break it down to use as a jump cue.
hi Greg;
I look to people like SVB who many consider to have the best 10b break on the planet and his bridge is closed. And it's powerful.
While I agree with you that accuracy certainly matters, I believe that varied levels of power also matter a lot depending on the game and rack being played. Wade Crane, Busty, SVB and many others all make a good case for high-power closed bridge breaking, imo.
best,
brian kc