One thing Jon said in the video I posted is that after reviewing thousands of videos now, what he's noticed is that people tend to shoot what they have in the gun. In other words, they're not reloading or reaching for a second gun. I remember him saying years ago in another video that it took him 1,600 videos before he saw a mag change, and he commented in this one that the mag change was done by a cop (trained as much). That said, they're just firing what they have loaded and stopping when they're out of bullets. So in essence, the outcome may be determined by the capacity of the gun and not in terms of carrying extra magazines in a smaller capacity firearm, for example (unless you're highly trained and going for the reload under pressure).
I also think what Massad Ayoob said was right in the other video posted above. The criminals are getting smarter. They're wearing body armour, they're outflanking law enforcement and making better use of cover (and forcing them out from cover), and more criminals are working in tandem than before.
I also agree with
Oldrider that I should have worded it differently. Perhaps I should have made the distinction between what the minimum number of rounds you want to carry versus how many rounds are in the gun, but I didn't stop to think people might include extra mags (especially after Jon's comment). I really meant this in terms of the latter (minimum pistol capacity).
And after seeing the Massad Ayoob video (thank you
HowardZ), I'm more of the mind more-is-better than I've been in the past. As such, I think I'm favoring my P229 with 14+1 rounds of .357 SIG or my Beretta PX4 Storm Compact with 19+1 which, believe it or not, conceals acceptably in nothing but a t-shirt (I can't say it completely disappears, but most people wouldn't notice it in my opinion).
After watching some of the scenarios in the video and hearing what Massad Ayoob said, I'd rather 15 rounds of .357 SIG over 18 rounds of 9mm, but I'd rather 20 rounds of 9mm over merely 16 or even 18 rounds of 9mm. That's just my take. But it takes 2 rounds on
average to stop someone with .357 and 3 with 9mm, .40 S&W and .45 ACP (
An Alternate Look at Handgun Stopping Power | Buckeye Firearms Association). If you do the math, that's 15 rounds of .357 Ă· 2 = 7.5 or 7 people versus 20 rounds of 9mm Ă· 3 = 6.67 or 6 people. It's very close one way or another, but 16 rounds of 9mm (15+1 like a G19 or P320 compact)Ă· 3 = only 5.33 or 5 people. I'm not trying to imply you'll be attacked by 6-7 people in a "flash mob" (Massad Ayoob's example), but I'm just showing the potential of the calibers & capacities. On the other end, you can empty a mag in someone hopped up on drugs faster shooting 15 rounds of 65 gr. .357 Underwood XD than 20 rounds of the 9mm equivelent.