All right, hypothetically...
Anything that carries five powerful rounds is more than enough. If you haven't immobilized the threat within three shots, he (if surviving) or his associates will have had time enough to immobilize you. So my choice would be my 296 or 696, or maybe my 649. Anything else on my belt or in my pocket is just extra weight.
Remember 3-3-3: three yards, three shots, three seconds. That's your average gunfight. Or so a wise man told me.
Never been in one. Hope never to be. But this is how I think of it.