Deflection can be a useful thing in a break cue. There is a point along any cue such that if you place your bridge hand there, and then pivot the cue about your bridge (intentionally or unintentionally), the cueball will still take off straight ahead, as if you had hit it centerball. In other words, the deflection (also called squirt) will just about exactly cancel the change in the direction of the cue.
A cue that exhibits high deflection will have this point relatively close to the tip, say 10"-15" from it, allowing you to bridge on or near it. For those of us that can't hit hard and straight at the same time, at least not consistently, this sort of cue can help with the accuracy of our break shots.
A low squirt cue (pivot point 30" or more) is considered desirable for general play, however, simply because it reduces one more variable that you have to compensate for. There are players though that having learned to adjust for it automatically after years of play, find an extremely low squirt cue to be problematical.
This is my first post here...I hope you don't think it should be my last
Jim