My .02 on .223 v 7.62X39
"IF" bad guys ever come to my door, they'll be met first by my "ferociuos" 11 lb. boston terrier. If she doesn't lick them to death, she'll annoy the S*%T out of them while I grab the goods and stash the wife & kiddo. But she's about as effective as both the .223 and the 7.62X39 IMHO, just simply annoying.
Just kidding...sort of.
I'm a .308 guy and use my M1A for everything short or long range so this is a non-issue for me. If you think you can't afford a .308 battle rifle think again, the Saiga rufle is an awesome weapon based on the AK rifle system and still available from Kentucky Importers for >$300.00. Hi-cap mags will be available this summer. If you've got alittle more cash, get a VEPR for about $650.00 or a little more....once again AWESOME weapon based on AK system.
If you've got enough $$$$ for an AR you can afford a Norinco M1A. Of course that starts a whole other "STALE" debate about Norinco vs. Springfield. My Norinco seems to shoot just as well as any other and if something breaks after 10 gazzillion rounds I'll fix it. That s what spare parts are for.
"IF" bad guys come to my house
at gang bang distance they will meet the Remington 12 gauge or the Volunteer Arms Commando Mark III .45 cal carbine. At >100 yards the .45 is just about as effective as both and I got 56 rounds in a drum.
To me this whole debate is summed up like this...choose the most gun you can afford and shoot it often enough to hit what your aiming at. When the hobgobblins come, ANY real gun you can hit with is better than a theoretically perfect weapon you've put off buying!