When LE started leaving the 9mm in droves, it was due to its ineffectiveness.
Not even remotely true, there are still some very large agencies issuing the 9mm and those agencies have had quite a bit of experience with the 9mm in shootings, and see no reason to move away from it. The move to the .40 was not becaue the 9mm was ineffective it was because it was trendy and the FBI went to it.
Its mostly about confidence in what we carry - and .40 gives me that over the 9mm.
There is no real world advantage of the .40 over the 9mm. if you want to believe there is that's fine. but it is just an example of perception dictating reality rather than fact dictating reality.