An actual, thoughtful response...I knew I liked you.
I like the idea that 308 can do just about anything. However, some Mk262 from a 20" or even 16" barrel can probably do 90% of what 308 can do inside 350m...which is probably max distance.
3-4k of 55gr 5.56 and another 2-3k of Mk262 is a pretty good chunk of heat...
Just to be honist I have both 223/556 and 7.62x39 in mass quainty and I still go to my AR platform for home defense.
Not because 556/223 is better than 7.62x39 but because I can get a Reliable AR for 400.00 and if it needs to be taken after a home invasion by the cops I am not out a ton of money and the rounds are plenty available.