So, you are going to be killed or seriously injured if you don't incapacitate your assailant right NOW.
Any other scenario does not justify use of lethal force.
Which weapon will accomplish that task the fastest and easiest?
Scoring multiple hits on target in a compressed time frame will be infinitely easier with a long arm than with a pistol. The .223 will make possible use soft body armor by your attacker a non-issue. The long arm being less maneuverable than a pistol is inconsequential because you should be camped behind cover waiting for help to arrive, NOT clearing you residence like a one man SWAT team. Over penetration risk of .223 is less than that of a 9mm NATO round, presumably because it quickly tumbles and fragments after striking most barriers; there are quite a few discussions on the topic.
Bottom line: Pistols are good for situations in which having a long arm accessible is impossible. For all other scenarios a long arm is the only logical choice.