A Revoler or a Semi Auto Handgun.
I started out in LE in the early 70s carrying a S&W Model 19 four inch and a S&W Model 60 two inch.
The Agency I worked for transitioned to Semi Autos in 1987.
I feel real comfortable carrying a Glock Model 19 or a Commander Sized 1911.
I also feel real comfortable carrying a S&W Revolver, depending on where I'm going and what I'll be doing.
No matter what I'm carrying, I always carry a Ruger LCP as a BUG (used to carry a Sig P230 and before that a S&W Model 60). Habit from my LE Days when a good friend of mine was killed in the line of duty when his handgun malfunctioned.