22lr, .22mag, .32acp, .380acp, .38 special, 7.62x25, 9mmx18, 9mmx19, .38 super, .357mag, .357sig, .40s&w, .45acp, 10mm and i may have forgotten one or two more...... i shoot all of those in handguns....
all have their uses...if i had to pick one i'd likely go .45acp or 10mm on the bigger side......or maybe 9mm on the smaller side. .40S&w is a fine cartridge. i consider it between 9mm and .45acp. with the right loads 9mm and .45acp can do more than .40s&w or at the minimum keep up...but that is splitting hairs in real world speak not talking about charts and data that doesn't mean too much more in the real world. so it's not a bad choice.....not the choice i'd make but i'm me and you are you.
good news is it's easy to convert to a .357 sig if you want, with a simple barrel change on some firearms......
said simply 9mm, .40s&w or .45acp hard to go wrong with any of those three......
having said all that rambling i'm carrying a .40s&w weapon today, so...........