I'm squarely in the 22LR camp. For me its about versatility and the weight of ammo.
I have two 16oz Nalgene bottles filled with 550 rounds (EACH) of 22LR in my Bug-Out Gear. I wouldn't want to venture a guess as to how much 1,100 rounds of 45 Colt or 410 ammo would weigh.
The Ruger Mk2 and Mk3 handgun is a survivalist's best friend.