3) Getting out of your vehicle with a long gun is definitely going to escalate whatever situation you decided you need a gun for and possibly bring in previously uninvolved parties. To most sheeple a handgun is a short range weapon, but anyone waving an AR/AK around is a "sniper" and the calls to 911 will be extra shrill.
4) The post-shooting media trial is going to be bad enough. Using a long gun is just going to make it worse.
I love this sort of logic. Introducing a handgun into a situation where there are knives escalates force. Are you saying that it is bad if you are the one who introduces the handgun because it escalates things? There was a very good reason for the slogan of "Peace Through Superior Firepower." Why is escalation a bad thing if it is needed to save your life?
I also like the fact that you have placed more concern on perceptions and post event antics than the battle and you have assumed you have won the fight with your handgun. Maybe you will. Maybe the handgun will be insufficient and you are dead afterwards and the media will still have a field day with your behavior and the family you left behind. You are counting your chickens before they hatch and you don't even have any eggs yet.
5) Texas still has that nasty liability law in place that says you can be sued for any damage done by a bullet you send down range. The chance of serious over penetration and down range hazards is too great with a rifle.
Actually, I don't know of any states that don't have a nasty liability issue that says you can can be sued for any round sent down range. Some states may not allow a bad guy you intended to shoot sue you, but others still can.
As for overpenetration, it all depends on what you hit with what ammo. Many rounds like 5.56 pose relatively small OP risks and even if they do, fragment or destabilize such that collateral downrange damage is greatly reduced. A .45-70 is another matter all together. Besides, you can go with a pistol caliber long gun such that you can have the better ability to hit targets at ranges typically greater than what you could do with a pistol as quickly or readily, but without much risk change to you and your liability concerns, but it depends on the ammo and what you hit.
6) A shotty is by far the best long gun for general purpose urban pest control, but items 1-3 tend to discourage me from keeping one in the car.
Once again, it all depends on a given situation. Shotties are great for many things, poor for others.