I'll take wounding for $200, Alex.
I don't shoot to kill. I shoot to defend, and it all depends on the situation.
Aiming for the biggest target?... That's what you do with paintball, airsoft and other imprecise toy weapons which may or may not respond the same shot after shot...
But anyone who is good enough to score a paper target inside 50' is going to be able to pick and choose what they're aiming at, be it a leg, arm, head, or torso. With a rifle, there's no doubt I'd hit a leg:
My instructor said a leg shot comes along with a higher guarantee they're not going to run away should you hit, and a shoulder shot means they won't be able to aim back... Firing in their general direction will also serve as a damn good deterrent, especially if you know what you have for shots remaining.
But a torso shot? They can still run, and they can still shoot, unless you've hit something substantial like the heart or the spine, and then you probably will have to live with the fact you've killed someone in self defense after you've stood scrutiny and possibly trial for homicide...