First we must separate the cue tip from the res of the assembly. Once we do this, most of the energy transfer has to do with the hardness of the tip, the weight of the cue, and the speed at which it is accelerated.
Given multiple different cues all weighing the same, the cue tip completely determines energy transfer (to the 98% level). The harder the tip the more energy is transferred.
Given a set of cues varying from light to heavy, there will be an range over which as the cue gets heavier the delivery speed decreases and the extra weight does not cause more energy to be imparted to the CB. This range in in the neighborhood of 18oz-20oz for normal adult males. Inside this range the hardness of the tip STILL determines the overall amount of energy in the CB.
So, in the end, the break is all in the tip (at the 85%-95% level) energy wise.