So I started to think about this after I had a wierd dream last night. Basicaly what it came down to in the dream was I was carrying my pocket .380, and had to engage two close range targets who were trying to carjack my little brother and I. In the dream I drew on both men, and while focused on the man to my left the man to my right pulled a weapon of his own. In my haste and confusion I ended up firing off all 7 rounds in my .380. I ended up running dry after striking both targets at least once, however not enough to drop them both. I ended up taking multiple hits from the gunman.
It made me consider a few things:
Is 7 rounds enough?
Is .380 enough firepower to drop a man?
Is a micro gun accurate enough that I can fire it and hit my targets under stress?
What do you guys consider to be adequete firepower, as far as caliber, gun size, and ammo capacity?
To answer all three of your key points, "It depends."
Many folks say that the majority of self defense shooting incidents only use up three rounds. Many also say that .380 is a bare minimum, but even a .22 is better than nothing. Accuracy of course will depend on a combination of the gun, the distance you're shooting, and your own accuracy and proficiency under stress.
That said, it sounds like this dream was pretty vivid, and that it certainly has garnered your attention. If it's something you are truly concerned about, perhaps you should look into a beefier sidearm solution. I'm not saying that you absolutely should make a change, but it can't hurt to hit up a shooting range, rent some guns in different calibers and capacities, and see where that leads you.
I've actually been looking into a .380 (in the form of a Ruger LCP) as both a backup gun, and as a 'primary' for circumstances where concealment is the #1 priority for whatever reasons. I personally won't rule the caliber out, as every caliber/capacity combination has a place and time, and sometimes it's just not practical to carry my normal piece.
For reference, my normal sidearm is an H&K USP in .40 with a JetFunnel installed and 16 round magazines. I carry with one in the chamber, the magazine fully topped off, and the safety off with the hammer down for a DA trigger pull on the first shot (SA thereafter.) I certainly don't "feel" outgunned with that setup, and I'm fairly accurate with it as well. My other rig for light concealment is an H&K P2000 in 9mm. Again, topped off, no safety, hammer down, etc. (13 + 1 rounds_ and again it's a rig that I'm comfortable with and able to shoot decently.
Regardless of the situation, I'd always opt for the larger gun (easier to control) with more capacity (more bang attempts) and a higher caliber round (bigger hole) if I can, but if it came down to it, I wouldn't feel a .380 to be insufficient. If I did, then perhaps I'm entering an area that's unwise.
Something else that might be of value to you regardless of the firearm you carry... more training. Seeing that you are in Vegas, you certainly have a few choices, and good training can help no matter what you carry.