I have watched quite a few Dash-Cam videos, of Police gun-fights. Oduls of emptying of pistols, with 80% misses, any calibre.
Does it really matter the calibre? Let's face it, the average Cop is a not very good shot, why? 100 rounds, every six months of "Training"
And they are not, on average, gun people. So does it matter 9mm or .40?
The days of 6'4" ex-Marine Cops? Is not so much nowadays, small people and females are the average Officer. With proper Instruction, they do fine.
Study all the gunfights that have happened, find the common denominators,
put that info into your lesson plans. Survival is the name of the game.
Case in point, I once had to vie for the ability to teach, and issue Diplomas of safe handling of first Double Action Revolvers, then into Self Loading 9mm Pistols, in Ontario, Canada. The governing body, The OPP Firearms Unit.
Purpose, teaching Security, and Armoured Car Attendants. For fee.
Taking two Sgt's from that unit on a class, was my in. Actually, they turned up with writing pads? My Classes were 8 students, always. My indoor range was only 10m wide, two lines of 4. I kept this class to 6, so as to fit the two Sgt's in. One on each line. That's about the maximum amount for one Instructor anyways. And in reality, you have only 4 to watch at a time, ideal.
They both had 20 years in, our two Sgt's and the first 6 shots at 7m were uniformly low left hits. I had an S&W model 10, minus a cylinder, and crane. Used for sighting, and dry fire purposes.
I would watch the trigger control, then line my eye, with students master eye (try for both eyes open) tip the back sight level, my eye and theirs, tip the front sight up to complete the sight picture. Felt good to know no go bang ability, you looking down the barrel, and all!
The report that went back to their Boss, "We learned more in 4 hours than we have done in 20 years of our Training!"
I was in, and for 25 years.