That's correct. However, a simple lack of evidence is not the same thing as a lack of evidence that persists after a concerted, prolonged and properly focused effort to find that evidence.
At some point, after decades of well-funded organizations and gifted people trying very hard to come up with proof and failing, it begins to makes more sense to work from the starting assumption that there's no proof than that there is.
Sometimes we can look in the wrong place for what we want to know.
What are we looking for proof of? (Or what is being asked for when they ask for "proof" in this case.) It's proof that one service caliber round may be more effective at stopping attackers then another. Lab proof. Proof that we can replicate. This is what Marshal and Sanow tried 20 years ago but lost their way on and went down a rabbit hole of One Shot Stop theory. Proof of that type will be impossible to obtain. One way or the other it can't prove anything one way or the other. It can't prove the 9mm is as effective than another round or prove it's less effective. Too many variables and too little verifiable evidence. But it's the wrong questions and an irrelevant one.
When some one says it's not proven that one service round has more effective terminal performance than another what they are saying is irrelevant to the discussion. Because that proof can't be found one way or the other. So we have to answer a different way, because the answer is there.
What makes one round more powerful than another and what evidence do we have of that? We know the answers to those questions.
Is a well placed shot better with a 9mm than a miss with a 10mm? We know the answer to that.
What bullet will do more damage to tissue and potentially make a more devastating injury, the 9mm or the 10mm? We know the answer to that.
Should we match the tool to the job? We know the answer to that.
Always choose the most powerful round that you can handle well from the gun you've chosen for a particular job. This is a simple way of approaching it and relies on the intelligence of the shooter.
We know that the .357 mag is a more powerful round than the 38 Spl. We know it can be carried in a wheel gun as small as a K frame S&W. We know we don't want to put a hunting round in it if our goal is self defense. We also know that it can be more effective as a self defense round than the 38 Spl. That's proven.
Sometimes it's better to carry a J frame snubby well concealed. Some times a 4" barreled 686 on the hip. Match the gun to the job.
We also know that many people can't shoot a 5 shot J frame loaded with .357 well enough to be sure of it for self defense. In that gun with our theoritical shooter, 38 Spl. will be a better choice for most, if the situation they are anticipating calls for that back up gun.
tipoc