We have had a love affair with the .45 since it came out, just like we have a love affair with the .38 spl, .357 magnum, .44 magnum. These cartridges, and others, have deep roots in modern Americana, and for good reason, they are all effective cartridges that our grandfathers, and fathers have shot. Even though the 9mm has become extremely common, many people still refer to it as the gun for girly men. As the .40 gains popularity, not much will change in the playful banter between those who carry and shoot .45 and those who carry and shoot .40 as the banter has never gone away from the .45 vs. the 9mm.
I like listening to people who have zero experience with firearms, and try to figure out where their information comes from. I have heard guys who do not own a single gun, talk about Glocks having no metal in them, not being able to kill with a .22, any cartridge other than the .45 being weak, all semiauto pistols being cheap and are throwaways that are not dependable, etc etc etc.
Bottom line is, shoot what you like. I like the .45 because I am a 1911 guy. Also, I do not want to stock too many different calibers of ammo. My non-1911 semiautos are also mostly .45s and a couple 9mm for cheaper practice. My first reloading cartridge will be .45 ACP. I have a friend who is the same way with .40s - he would rather only stock .40 ammo, so he is realigning his collection to only include this cartridge. Whichever cartridge you have - if you can shoot it effectively, it is common enough to find if and when the SHTF, and it is a quality and effective cartridge, and is not way underpowered, then go for it.
I would not want to be shot with a .40, even if it is a kid's round.