There is no one right answer.
For very small carry options, I have an odd fondness for the Kel-Tec P-3AT. It’s the worst of all pocket pistols in terms of shooting, and it’s the worst imaginable firearm for a gunfight. Outside 15 feet, it definitely needs a laser. On the other hand, the Kel-Tec is a firearm and that’s a hundred times better than no firearm. It measures 0.77 inches thick and 8.3 ounces (11.2 ounces loaded). With a laser, a full magazine and a pocket holster, it is literally the dimensions and weight of my iPhone 7 in its slim protective case. Every other choice I’m listing shoots better, but what the Kel-Tec gives you is a firearm instead of no firearm for those situations where a larger/heavier carry choice might not be convenient. No one would ever leave the kel-Tec behind because it’s too heavy or bulky. No one would ever guess you are carrying with the Kel-Tec.
Only slightly bigger and heavier but much better shooting choices include several very small guns I thought felt comparatively nice, under 20 ounces, and under a certain size measure. Listed in order by size from smallest to largest, they are:
Ruger LCPII in .380 [Note: I hate the trigger on the slightly less expensive LCP - it’s just a long, awkward pull and uniquely difficult to keep on target]
Kahr PM9 in 9mm
Glock 42 .380
Kimber Ultra Carry .380
Ruger LC9 Pro 9mm
SIG P365 9mm
Somewhat larger options that are even better for shooting, just bigger and heavier:
Glock 43 9mm
Springfield XDs in .45 Auto (heavy compared to the rest, but it’s small for a .45)
Ruger LCRx .38 Special
Other than the Kel-Tec, which I thought deserved special description because of its unique size and weight, I’m not taking the space for detailed descriptions. These are some of the guns I looked at when I was shopping for a small carry weapon, and I liked each of them enough to seriously consider a purchase (I now own several of them). I’ve shot them all and would be comfortable recommending that any of the above be considered for concealed carry.
For any of the above, I very strongly recommend a good holster, even for pocket carry. For Glocks (I own several and love them, but the fact is moderately knowledgeable people make more mistakes with Glock than with everything else combined), I recommend watching the Glock “oopsie” videos online before carrying - and using a good holster, and carrying empty chamber unless you NEVER get careless or clumsy. I have never had a negligent discharge, but I treat my Glocks with special caution.
For pocket carry, I use the original LCP or my S&W 60 (357) revolver. Can’t imagine a revolver guy thinking the LCP has a difficult trigger. I prefer to carry the 357 in an Uncle Mike’s holster clipped to keep the grip out of the pocket. Then cover it with an untucked shirt. Shooting 357 with it at the range is no fun, but I doubt I’ll notice any recoil if I need it for real.
I have some of the guns listed in the article. Two of them I especially love.
I have never trusted .380. I carried a 25 pocket pistol for years, it was accurate for 15 or 20 yards but not deadly at that range.
One of my kids (a cop) got an inexpensive Kel-Tek 9mm. It came with a belt clip. He didn’t like the double action only and sold it to me for cheap. I had a problem with it and Kel-Tek repaired it for free. It shoots straight and true. Interestingly it came with a belt clip. I do not use a holster, it clips onto my trousers and what very small portion sticks up above my trousers is hidden by my shirt blousing over it slightly. It replaced my S&W Shield that holds an extra round but hides about the same perhaps a little better but this is substantially lighter.
I never liked carrying the S&W because of the size and weight but I never even think of the Kel-Tek, sometimes I have to feel with my hand to make sure I put it on.
Whatever weapon you choose make sure it is something you will carry. I always recommend you get a double action only weapon for safety sake. You have to practice more with it to be accurate but you won’t hurt anyone unintentionally. A weapon does no good in your car or in a drawer at home if you are not at the drawer or in the car.