Just to throw my two cents in here:
I'm a pretty strong guy, nowhere near as jacked as I want to be, but still in the upper levels of strength for your average guy off the street (I'm 6'0 180 and 20 yo).
I decided to experiment with the weight of the cue as a factor in breaking this summer using house cues that my friends set up in random order from 17-23oz. I tried to stay as purposefully ignorant to the cue weight as possible, but since I shoot with 18.5-19oz cues, I had a general idea of what I was holding during the experiment.
In echoing an earlier post, my results were largely the same regardless of the weight difference in terms of breaking success. I didn't have a spedometer but I "measured" the success of each break by spread, consistency and number of balls pocketed. I know I went about this in a very unscientific way, but my general conclusion is that, at least for me, the weight of the break cue really doesn't matter. I currently break with an 18oz cue and generally like to grab a 19oz or lighter house cue to break with when I'm traveling with just a 1x1, but I don't think it would make much of a difference if I used something in the mid 20's either.
Although I can't say for sure for players of different sizes, I don't think that the weight difference would matter much for most players in general either (staying within the bounds of common cue weights - we're not talking about 40 ouncers here). When you think about how the weight of the cue is applied (again, referring to the ubiquitous f=ma equation) the difference in ounces is rather minute because we A) use a bridge, lessening the burden on our arm that is doing the propelling (the dominant arm) and B) we move the cue a relatively short distance. If you're not following me, think about how heavy your cue feels when you're practicing your stroke vs. how heavy it feels holding it with one hand swinging it side to side. We don't ever encounter this movement in pool (unless you have an Earl Strickland length fuse =P) and by comparison I think that the difference in cue weight is really exposed as almost insignificant.
If you want to take the physics out of context, then sure, all things remaining the same the heavy cue will win out every time with the same acceleration - that much is obvious. But as things get heavier, there is a naturally greater resistance to movement that must be overcome - it takes longer to accelerate than a lighter object of the same dimensions. For a bigger guy like me, this shouldn't be a problem, the heavier cue should still win out, but think about the parameters of pool for a second. How much room do you actually have to accelerate in a break shot? On top of that, how many (or, perhaps more appropriately, how few) muscles and how much weight actually goes into a proper shooting motion?
Like most pool players though, I'm only an innate physicist - the subject is far from my strongest suit (not to mention the fact that I haven't studied it in three years). Like I said at the beginning, this is just my two cents. It may be that this weight indifference only applies to people built like me. However, given our disagreements with practically everything debatable in pool and the lack of a concrete answer on this topic despite all of the discourse, I'm more inclined to believe that once again, it's probably just personal preference.
