In this thread you have a Glock 20SF and a Glock 21 SF. 20SF is 16 rounds of 10mm total capacity 21SF is 14 rounds of 45 acp total capacity You can carry a spare mag with either pistol. You already have lots of your favorite SD ammo for both, so ammo cost nor availability is a factor. You shoot the two pistols equally well. Which pistol would you prefer for SD against humans? Replies that it makes no difference, 9mm, Glock 19, those pistols are not concealable, (off topic) are a waste of keyboard and internet. Yes, I do have both, so the choice is real.