My experience in heat of the moment situations is that you are not going to be remembering what round is chambered in that situation anyway, you'll be in full adrenalin dump mode and pulling the trigger as fast as you can get your sights on the target. A slug seems silly if you're worried about over penetration. Go with larger shot, #2 or larger or low velocity (tactical) buckshot.

I would avoid the flite control at HD distances. It patterns around a fist size for me at 20 yards in open chokes. Regular buckshot gives a little more spread, like dinner plate, at that distance. But you want the low velocity stuff.

Also remember you might be shooting through a section/corner of interior wall (on purpose) or furniture (on purpose) to get the bad guy. What you can bet on is he will not be standing there, square to you, offering himself up like a target at a shooting range. You definitely want more than birdshot penetration, in my opinion. But less than slugs. Which seems to be the general consensus.