There is no such thing as knock down power.
I think that the .45 is more common, but the 7.62 is cheaper if you shop around.
All guns (calibers) can kill.
The "deadliest" caliber, in handguns, is the 22lr.
More people have died from this caliber, nationwide, in the last 100 years, than any other fired from a handgun.
But dead is not "knocked down", as in, ""I shot him once, and he fell like a puppet whose strings had been cut.
That can happen, if you severe the spine, with any caliber.
But no handgun round, that is available in a carry gun, is powerful enuff to "knock someone down".
All due respect to sksmedic, but simply viewing the aftermath of a shooting does not tell the whole story of what occurred.
I too have been on site of a few shootings, as well as read the after shooting reports and debriefs, and attended autopsies.
I've even been present at several shootings, while the bullets were still flying.
Saw a person hit with a 12 gauge slug, who remained standing and combative for at least 20 seconds.
If a 12 gauge slug, at 438 grains and 1600 fps, with a caliber of .69, can't be relied upon to immediately terminate an attack, by "knocking down" the aggressor, then a 45ACP, with 185 grains, at 1200 fps, and a caliber of .45 certainly can't.
(45ACP Ball ammo is
superior to 9mm Ball ammo in it's ability to end a fight)
The Tokarev round (7.62x25mm) has slightly less ME than common 9mm (non plus P) rounds, and unless dangerously overloaded, is not comparable to 9mm+P.
9mm+p, with modern JHP ammo, is as good a SD round as any 45ACP, 357, Sig or Mag, 45ACP, 40S&W, or any other such caliber, all recording 90% or better on what is sometimes called "one shot stops", which is defined as ....one round, placed into a vital upper torso area, with a result that the aggressor becomes non-combative within 10-15 seconds.
Which is, or should be, meaningless to a person defending themselves, as you should fire for effect until the threat is gone.
10 seconds is a LONG time for a person to be able to shoot at you.
To most experienced persons, this means at least two, and likely three shots.(and sometimes, more)
At that point, with any of the better calibers mentioned, you should have negated the threat, if you placed your shots well.
If you missed, or did not stike vital CNS or CP systems, you might yet be there a while.
I'd stick with something shooting the 45ACP, between the two guns, for energy and logistics purposes.
The 1911 format is fine, but there are more modern,and equally as good, options in handguns.