Regarding the 5.7x28mm...
Being an owner of a S&W .22 Magnum revolver, and having an opportunity to run 100 rounds of 5.7x28mm through a FN Five-Seven pistol, (at a cost of $68.50 USD!), I can attest that the 5.7 dwarfs the .22 Magnum across the board.
Not really. The .22 WRM out of a rifle barrel is ballistically similar to the 5.7 out of a 10" barrel. They are similar, not exact, but I wouldn't call it dwarfing, by any means. To split hairs, the 5.7 is more powerful, but not by a massive margin. Obviously, the 5.7 is better at armor penetration, which is what it was designed for.
Finally,
...all I can say is that given the choice between the two, I'd never opt for the 9mm over the .45; all the "trick bullet" hijinx the 9mm relies on, (almost all of which isn't applicable to military ammunition), the .45 can do, too. But, if that voodoo doesn't work as designed, (and, that does happen), the .45 is *always* bigger and heavier. Your point on magazine capacity is perfectly valid, but I was taught to shoot not on the "how many" concept, but rather, the "where you place them" method. There are reasons why the .45ACP round endures, and the popularity of rounds like the .40 S&W (10x22mm) grow.
I was trained that shot placement matters more than caliber. The "how many" is irrelevant, as with any caliber, I am going to keep shooting until the threat is neutralized. The .45 isn't a magic bullet, and all handgun rounds are marginal stoppers. I'd opt for 9mm over .45 for the fact that the ammo is lighter, I have more of it, less bullet drop, and importantly, less recoil. Faster followup shots matter, you will be shooting someone more than once.
In actual shootings, and statements from doctors and coroners, most all of them stated that they couldn't even tell what the victim was shot with until they dug the bullet out. On paper, the .45 is better, but for all practical purposes, you aren't likely to see a massive difference between 2 of any of those rounds center mass, in overall effectiveness.
Hollowpoints are not "trick bullets". It is simple physics. The reason the 9mm is "weak" is overpenetration. The hollowpoint causes a larger wound channel, and allows the bullet to dump all its energy into the target. To overcome the "problems" with military ball, you practice 2 in the chest, 1 in the head anyways. I would do that with any handgun caliber, ball or hollowpoint.
I had a .40, but got rid of it because the snappy recoil was annoying, with carry ammo.