The more you kill the less you rely on power and the more you rely on placement, I think. Commonly, the folks gunning the most powerful armament don't have many kills under their belt. Of course that is an oversimplification but confidence comes with experience.
On the money.
Mike & sb -
I agree in principle in that WT are the largest big game I've had the privilege to hunt. I know exactly what y'all are saying is true but I would like to add this caveat, 'Faster' cartridges allow flatter trajectory, making placement easier at longer distances.
I am NOT speaking nor recommending 'long' range shooting of bear. That's out of my wheel of experience.