It depends... I use airguns to plink and shoot ground squirrels in the pastures. Used to use center and rimfire rifles and pistols for this duty but overpopulation has made that impossible. I shoot out to 40 yards mostly so either caliber works, however, I do want humane kills and I'm a firm believer that big bores are better in this regard. Velocity does kill it's true but a .22 caliber hole in a critter the size of a groundsquirrel makes quick work of them.