I think when it's all said and done, you have to go with what you're comfortable with. My personal preference is 9mm, it just is. Namely because I see a handgun as a way to create space between myself and an offender until I get to a shotgun.
A tactical shooting instructor told us once "Let's face it folks....getting shot !@#$%^& hurts" meaning ideally you want a center mass double tap, but hitting a shoulder, knee, neck, hand, ankle anything to get some distance.
We could debate the ins and outs of every round made, to me, a handgun is simply a way of me teaching an offender healthy boundaries.
No it's not JUST about survival, but initially it is. You have to take into account the ideology, that anyone you add on to your team, can become beneficial, AND a liability. The first rule in rescue is you cannot rescue anyone if you're dead yourself, so instinct tells us "take care of yourself FIRST". When the dust settles, I would think seeking survivors (if they do not find you first) is a good idea, but realizing that someone will have to assume leadership. Communal rule seldom works in emergency scenarios.
Bugout, find shelter, hunker down, survive at least the first 72 hours. Then become a community organizer :)
You can stock a reasonable amount of supplies in your home, you can stash here and there. We use a closet that is infrequently used at all, a walk-in. So it's room temperature or below, and large enough for our entire cache of bugout supplies and MRE's. The issue I have with storage buildings, is it could get crazy enough to consider even the owners of these places declaring your stuff theirs. I do not want to have to shoot my way into a place to get my own stuff.
As selfish as it sounds, they would have to bring something to the table, skill, food to share, intel, ammunition etc. Once everything falls apart, it's about building the best team, forming loyal alliances. Not feelings.
Family first, all others must have SOMETHING to contribute to the group, a skill, a resource, or location of resources. It is after all survival, it's not a popularity contest.