One of the drawbacks in living is such state is magazine limits.  If all you can use is a ten-round magazine, then a full-size 9mm is overly large for the capacity.  Other than ammunition costs (9mm practice ammo is really cheap now), you might as well carry a gun that shoots bigger bullets.

The original wondernine, the Browning High Power, is a good example. The standard 9mm held 13 rounds.  The .40 S&W variant, which had a fairly short production run, held ten rounds.

The S&W 3rd generation compact 9mms held 12 rounds.  The .40s held nine.

But let’s be frank:  The old debate over caliber size is utterly passé.  There has been enough work done that shows that the difference between an expanding 9mm and a .45 is maybe one or two tenths of an inch.  Handgun bullets incapacitate by penetrating deeply enough to hit vital stuff.  A down-right-now hit requires hitting the central nervous system, which is a small target and is at the back of the body.

As an aside, Lucky Gunner compared a lot of different rounds.

Velocity, out of handguns, matters for two reasons: Pushing the bullet out fast enough so it expands and so it penetrates enough.  Clear ballistic gel tests can show impressive temporary stretch cavities, but research has pretty well proven that unless a bullet hits at over 2,000 fps, a body isn’t affected by that.  Over 2,000 fps, there is tearing and other bad stuff, which is why a 5.56mm round at combat ranges does what it does.

But to the point: If you can’t carry all of the 9mm rounds that a gun can hold, you might as well carry one that holds bigger BBs.