First the caplock was developed to give more consistent ignition in less than optimum weather, for MILITARY applicaltions. The locks themselves are much simpler and more durable in design, again making them an advantage for production in military arsenals.
When talkin' target shooting, you look for consistency, and the shooter makes up for the rest. The "problems" with a flintlock is the higher number of variables lean to a better chance at inconsistency when in target competition. That's all.
I have seen a bunch of flintlock tests, though I admit to not having seen or read them all. I think they are nice to show what a flintlock can do..., I don't know if they show what they often will do. Ya see they are all done under laboratory conditions. New locks, dry enviornments, a couple of tests that I saw used a hot wire as an ignition source. While this makes the test uniform and consistent, it doesn't recreate actual shooting conditions..., unless we all hunt and shoot in laboratories?
Accuracy tests, and ignition tests, all remove the human element, and fire from static, solid positions, but we then hand the firelock (be it caplock or flinter) to a human to shoot it outside the lab, and often don't use a bench. We add a whole bunch of additional factors into the equation, and say "we know the truth".
Things they don't account for in testing:
Every time the flint hits the frizzen the surface of the frizzen as well as the edge of the flint changes, and that can have an effect on firing...,
We use new locks, new barrels, as near to perfect as we can get alignment between touch hole, lock, and trigger, but don't account for what happens to a rifle after say a decade of weekly firing...,
Prime in the pan absorbs moisture from the air over time, and 4Fg absorbs it faster than 3Fg, etc...
The atmosphere we fire in has variable humidity over time, altering the speed of moisture absorbtion by the prime...
Electronic ignition has no moving parts, bolt guns move toward the muzzle when releasing the firing pin, but caplocks and flintlocks move on the side of the barrel in a arc..., has anybody ever tested to see if the motion of the hammer or cock moves the rifle in an odd manner depending on the lock design?? Inertia is inertia, and when the hammer or cock is released, it moves and strikes another part of the rifle? Does that give the rifle a tiny "twitch"? Which lock is better or worse at causing this movement? Does this movement matter when fired by a human? Does a flinter dissipate that impact as the cock strikes the frizzen which moves and absorbs part of the impact prior to the cock coming to a rest on the lock plate..., while a caplock just drops the hammer against the cap supported on a nipple, installed in a drum attached to the side of the barrel?
AAAAAAH my head hurts!
Bottom line (imho), a flinter can be just as fast if not faster than a caplock..., but there are more variables that can interfere with igntion to cause inconsistency. I think with less variables it's easier for the average shooter to master the caplock vs. the flintlock, hence the higher popularity of the caplock, that's all.
LD