Seems logical to me that if I can throw a small stone faster than a

brickbat I can, with very short stroke in relation, get more speed out of the lighter cue. The same force applied arm strength will result in faster speed to the lighter object or am I wrong and why.
In a PURELY theoretical world, a lighter cue results in more cue ball speed and energy.
If a compressed spring launched a heavy cue in space, the heavy cue would have greater mass, slower speed, and a kinetic energy of X, equal to the potential energy of the compressed spring.
If the same compressed spring launched a light cue in space, the light cue would have less mass, faster speed, but the SAME kinetic energy X, the potential energy of the compressed spring.
It can be shown mathematically that a light cue will transfer a higher percentage of its kinetic energy to a 6oz cue ball than the heavy cue will.
But as other posters have noted, we are playing in the real world. There could be limits to the speed your biceps could develop, regardless how light the cue is. Plus, when you consider the mass of your arm and the slight difference in weight between cues, I think the difference in CB speed will be small.
Ultimately, I agree that accuracy is the most important thing. Use whatever weight feels good and gives you the most control.