I own .38 Special, 9mm, .40s, .45 ACP and .357 SIG.
I carry 9mm almost exclusively in an urban environment. Here is why it makes sense for me in that situation:
1. I'm carrying Speer factory 124 gr Gold Dot +p which has a proven street and lab record. There is nothing boutique about it and if it is ever a legal question I can point to several major metropolitan departments with thousands of officers that carry the same load.
2. The wolves travel in ever larger packs these days. For a given size firearm I want the most on tap within that platform that I can have, before a reload is required.
3. Given the above point and that I tend to carry smaller pistols because of my personal logistics, the 9mm meets that requirement better for me. Yeah, I know it's usually only a round or two difference in most cases but I'll take it. Shot placement is king but in a dynamic situation with less than ideal shot placement I'll take the cumulative effect of two less than ideal hits with a 9mm over one less than ideal hit with a larger caliber. (Except 10mm which is known to lift the assailant clean off their feet with even a thumb hit, but it violates the Geneva conventions
4. I'm a civilian and I don't work in and around vehicles all day so the heavier caliber's auto glass performance is not a factor for me.
5. I can shoot 9mm fast and accurate. In a me vs me comparison I will always outperform myself using 9mm versus another service caliber. Now I might shoot .40 or .45 faster and more accurate than another guy shoots 9mm but I can always out shoot me vs me using 9mm. I could shoot all year with a G27 and be damned good but at the end of that year I would still shoot a G26 that much better.
6. The firearms that I carry most often were all originally designed around the 9mm. I have a gut feel belief that carrying a firearm in the caliber it was originally designed for gives the best reliability and lessens the chance of a freak parts breakage at a bad time.
Do I think the .40 and .45 ACP are more effective by a degree or two? Yup. But given my above perceived personal requirements and situations I think the 9mm is my best choice for most of my carry situations. I think .357 SIG smokes them all in the common service calibers and if I was going to ditch the 9mm for everyday use (I'm not) I would go that route because it somewhat duplicates the famed 125gr .357 Magnum but in a platform that would work for me from a practical carry perspective.
I do carry other calibers in more rural settings but then I usually do have a shotgun or rifle right there so it's moot.