The answer to this question may be debatable but personally i rate the 9mm.as the most suitable and versatile in the sense that it can be used by other members of the family i.e. wife,teenage son & daughter.As far as stopping power is concerned it may be on the lower side as compared to a 45 or 357 mag.but then these weapons are not easy to handle and require lots of practise.
The other gun that i prefer and sometimes carry is the 32mag.snub nose by Charter Arms.At close range this one is lethal,especially when using hollow points.
What are your preferances.