Therein lies the problem that I see with 9mm: it's more dependent on choices of gun and ammunition to get "sufficient" performance than bigger, more powerful calibers. The way is see it, "sufficient" performance in 9mm is dependent on three factors of which you need at least one and preferably two: a 4+" barrel, modern premium ammunition, and +P or +P+ ammunition. All of my 9mm pistols have 4" or longer barrels and I have no qualms about relying on them with my chosen ammunition like Federal HST, Speer Gold Dot, or even the old Federal 9BPLE, but were I restricted to one of the new micro pistols and generic standard pressure Winchester White Box, Federal Hi-Shok, or UMC JHP's, I'd be a lot more comfortable with a bigger caliber.
While these modern bullets are usually easily available, that really shouldn't be counted on as just a few years ago we all went through a period where ammunition of any sort was scarce, much less hand-picked specific loadings. Also, this wasn't the first such ammo drought and, given the state of politics and world events, likely isn't going to be the last. While it's always a good idea to have a decent supply of your chosen ammunition on hand to get through "dry spells" when they occur, premium ammo is expensive and not everyone can afford to buy a case of HST's "just in case". For these reasons, I can see the logic in someone choosing something like .40 S&W or .45 ACP because it will still work "sufficiently" even with old-technology JHP's.