Let's just say you could only use 1 caliber for home defense - the 9mm or 45acp. Let's just say you shoot them equally well out of gun "X", recoil is not a problem with either, and both guns "fit like a glove". In the 9 you would be using 124gr +P Gold Dots and in the 45 you would be using 230gr Gold Dots. The 9 would hold 17+1 rounds and the 45 would hold 10+1 rounds. I know this is the age old debate - but which gets your vote for home defense? (Oh btw, brick home, not an apartment, no kids, dogs or cats running around).