The chances of breaking your bat will increase with wanting to change the momentum of the ball. That includes not only a change in the speed of the ball, but also the change in its direction/angle. Hitting a straight drive will increase the chance of breaking, whereas playing a leg glance or a late cut will decrease the chance of breaking. A block stroke will be somewhere in between.
(Note that a block stroke, although usually played with a light grip, is not intended to "catch" the ball and reduce its speed. Rather, it is intended to change the direction away from the stumps and downwards.)
To hit a "six" (a cricket home run), you actually don't have to change the momentum of the ball too much (and risk breaking your bat). Youtube shows you how it's done with the Dilscoop: "That's using the pace to your advantage."
(Taken from here.)
In practice, the best ways to break your bat are to play with a dried-out bat, jamming the ball between your bat and the ground whilst attempting to hit a fast yorker, and hitting a rigid metal object (in the nets). I've done all.