My favorites are not the same as what I think are the “best.” I could nominate .45 ACP as a best, and a favorite. My first handgun chambered .45 ACP. The .357 Magnum could be a best, and, a favorite. My favorite individual handgun, visible in my avatar, is a .357 GP100, and was used in a defensive incident. Both .45 ACP and .357 Magnum have been duty pistol cartridges, in my personal past. (I worked as a big-city police officer, for 33+ years, and am now retired.)
9mm would be a cartridge that I consider a best, but would not necessarily be a personal top-three favorite.
Aging has caused recent shifts in what is suitable for my hands to continue shooting, and social isolation, made necessary by the panic-demic, has inhibited my ability to test some potential new bests, and potential new favorites. I already traded-away my Glock G19 pistols, in 2020, when they became too much, for right thumb and wrist. (Actual swelling, that persists; not just discomfort, though, thankfully, full-sized 9mm Glocks remain my “orthopedic pistols.”) It remains to be seen whether I will continue to shoot my 3rd-Gen S&W Nines. So, whatever votes I cast, today, are subject to change, whenever we can safely visit shooting ranges, again. (My wife is at a higher-risk, so we are all the more careful, regardless of local emergency orders and procedures.)
Past top-tier favorites have fallen from that height. The first to tumble was .44 Magnum, in 1985, when I realized it was a just a bit much, for routine use. I shifted attention to the .41 Magnum, for police duty and for personal carry, for about five years. I finally admitted to myself that I have K/L/GP100-sized hands. I was an early adopter of .40 S&W, in the early Nineties, for some personal carry, and used it for police duty from 2002 to 2015, when it was the employer-mandated standard. But .40 S&W was battering my aging hands, by age fifty, and I was able to start using 9mm while on duty, in 2015. I have not fired .40 since 2014.