There will be lots of differing opinions I'm sure. Mine is based on what works for me. I would sometimes pocket carry a Glock 26 9mm (in a pocket holster of course.)
It was heavy and felt like a brick.
I bought a Kel Tec P11 9mm...like it so good that I sold the baby Glock. The Kel Tec is lighter, shorter, thinner, and has the potential for a higher mag capacity without adding magazine extensions. It also feels better in my hand than the Glock 26.
I bought a couple of the Kel Tec (Mec-Gar) 12 shot magazines. That gives me 12+1 in a pocket sized 9mm.
I've never had any shooting issues with the Kel Tec...feeds everything I put thru it with no problems. I'm not comparing the quality of it to a Glock, just the size and thus far reliability. The trigger pull is similar to shooting a double action revolver.
Here's some weight comparisons (loaded) and pics of it with a couple of 5-shot J-frame S&W pocket guns.
S&W 642 with 5 .38 specials weighs 17 ounces
S&W 49 with 5 .38 specials weighs 24 ounces
Kel Tec P11 with 13 9mm's weighs 23 ounces
You can go even lower in weight (and magazine capacity) with the single stack Kel Tec 9mm...I don't know that model number. But, I like the thoughts of 13 rounds of 9mm +P JHP's riding in my pocket.