You, sir, are correct. But a lot of the people posting in this thread don't understand, or perhaps choose to ignore, the "effective firing rate" component.

I used to carry a .40 -- did so for a lot of years. But with today's 9mm ammo, I'm more comfortable with a G19 than I would be with a G23. I shoot the G19 faster, and it holds more ammo.

The "old" conventional wisdom was to carry the biggest caliber you could "control." Today's top-tier instructors will tell you to carry the caliber that lets you shoot at the fastest rate of fire while still getting good hits.

I see a lot of students who think firing one shot every five or six seconds is an acceptable rate of fire for self-defense. Anybody can do this with a just about any caliber handgun -- and that's hardly the goal one should strive for.

Muzzle flip is a consideration in picking a SD caliber -- 'cause that's the biggest factor in achieving (or limiting) our rate of fire.

I'll go out on a limb here and say (assuming one maintains the same level of accuracy) that 99% of us can shoot a 9mm faster than we can a .40 (in the same frame gun, like G19 vs. G23). Similarly, we'll all shoot a .22 faster than a 9mm, but the point of significant diminishing returns comes into play quickly with a handgun chambered in .22 LR.

Anyone who has practiced, or shot in competition, with an electronic timer has easily seen the effect of muzzle flip on handgun rates of fire. They have also seen that 1 shot every 5-6 seconds is really slow (and that 4-6 shots per second is achievable, with practice, depending on the degree of muzzle flip).

p.s. 9mm practice ammo is a lot cheaper than .380, .40 and .45 caliber practice ammo. This should enable those who don't have unlimited training budgets to achieve a higher level of proficiency with a 9mm (all other things being equal).

Just my $.02 worth.