A round in the chamber is essential no matter what you carry.
I carry a 1911 when I have to carry an Auto. It is as fast as a double action revolver, more pointable and powerful enough. You still have to chase brass and a few personal dislikes that don't matter to others.
A single action revolver is the fastest first round handgun, but not practical for Burb Carry.
Police like the .40 and high capacity. Many don't shoot well and that's where the phrase "Spray and Pray" came from. Solid, first shot center mass or center groin, shots come from practice. Thousands of rounds from every position possible. There isn't any substitute.
I have a special dislike for the .40. The guns chambered for it are generally smallish and light and the little high pressure cartridge gives too much recoil for them...and the brass is usually unsuitable for reloading.
I collect the brass at ranges to swage out and use as jackets for my 45/70 bullets.
My first choice in a cartridge is the.45 Colt but it's hard to find guns that can be tuned for acceptable double action work so my second choice is the .44 Magnum.
The bottom line is you have to find a gun/cartridge that works for you...
Then shoot it a hell of a lot.