It's 7AM and I am posting some "laying awake at 3AM" thoughts, so bear with me.
All 3 will get the job done, that's a fore gone conclusion. But doesn't purpose enter into it some what ?
With rifles we want to teach a certain range of distances and penetrate a specific target. For example, hunters need to penetrate meat and bone to teach vitals, while military shooters need to do the same after penetrating clothing web gear, and possibly a certain level of protective gear. Cartridge sizes started out in the .45 caliber range for these purposes, and for big dangerous game, I will grant they have stayed there, (yes, Karamojo Bell hunted elephants with a 7 or 8 mm, but he also preferred an ear hole shot) as bullet and powder technology advanced how ever bullet diameter dropped to 6 mm (1898Lee -Navy ) and the current 5.56/5.45 fad but preference has stabilized in the area of .30 caliber as the best combination of velocity and bullet weight to get the job done at all ranges .
Pistols have a different purpose . Relatively short range, stop 'em NOW. Not necessarily immobilize, or kill, but STOP. It seems that a really heavy, not so fast bullet. would be more appropriate for self defense, since as a general rule of thumb any one the law justifies shooting is going to be close enough to injure you or recieve the loot a victim is expected to hand over.
I'm thinking, start at .50 GI and work down to the largest caliber you can shoot well (and afford to feed) .
Remember before you light me up that these are late night thoughts written early in the AM

My personal idea for a great pistol would be a Walther -P 38 double stack, .45 with the controls and grip angle the same as a 1911 , Tritium, or TFO sights, and a barrel with integral suppressor.