Situation #1 - existed for me when I got my first gun, and it was a .22 pistol. Doesn't exist for me, unless finances get so bad that I have to sell all my guns to feed the family/pay medical bills/something like that. I would keep my 642, because most recreational stuff would be going out the window as it would be a survival situation for my family, and keeping a gun that I could carry all the time would be my primary consideration.
Situation #2 - I would carry two or three guns. One would be an AR, and the other would be a big 9mm, and then my 642. Sorry, but I can't see me going with only one in that situation. And I'd have more than 100 rounds of ammo, too.