OK, so you are not interested in discussing firearms as survival tools. That is certainly a point of view. You might find it a less than useful point of view in some scenarios. Depending upon your estimation of the likelyhood of ever having to face these scenarios your view of the need for firearms will be different. Let's run through some of these scenarios.

1) Dropped in the wilderness and need to collect food since you will not be getting out this week. Yes, you can use snares until they run out. Yes, you can eat nuts, berries and mushrooms until you poison yourself accidentally. Yes, the firearm will only help until the ammo runs out. Nonetheless, the firearm is moderately helpful here. Which you choose is a matter of quite interesting discussion after you accept the utility of the tool. Many think that the shotgun is a decent tool for gathering small game and large game with the same tool.

2) Large scale disaster (terrorist attack, severe storm, volcanic activity, tsunami, asteroid impact, anti-war protests) results in breakdown in the rule of law and you can no-longer depend upon the law enforcement individuals to protect you with their weapons. This might be due to damage to roads or to the general lawlessness of riots. In this situation a firearm is a tool that some would consider useful in protecting the preparations that they have from the appropriation of others. If you accept the utility of the tool then discussing whether the shotgun is better than the .45 handgun is appropriate.

3) Intruders from burglars to those with personal homicidal intent. These situations can not be met without some sort of defensive plan. Giving up you stuff may satisfy the common burglar but will do nothing to defend you from someone with true maliscious intent. The police will attempt to find and bring to justice the criminal after - AFTER - they commit the crime. This does nothing to prevent the crime other than engendering a general sense of danger to the profession of the criminal. Unfortunately criminals continue to exist in all societies in spite of this danger of being brought to justice. Again, if you accept the utility of a firearm in such a scenario the discussing whether a shotgun is better than a .45 handgun is appropriate.

These are not an issue of this policy of this site but rather more related to this statement on urban preparedness.