The Answer
I'm not some high speed, low drag operator. Just a 72 year old that has been "around the block" and carrying as LEO/legal civilian for over 50 years and with a "serious social discussion" or three that occurred in the early 1970's (all LEO/duty related). Were there times when carrying concealed (off duty/CHL) in which I was glad to be armed or had to draw, yes. Fortunately, bad guys/dummies made the right decisions.
I've carried a BUNCH of different pistols and revolvers (remember them?) of various makes, models and calibers over those 50+ years. Which one was the best, you may ask? THE ONE I HAD WITH ME AT THE TIME!!! I do have some "pocket" handguns, in every thing from a .22RF (long only, talk about wimpy), .22RFM, .25ACP, .32ACP, .380ACP and even a 9m/m SIG 938. But, ANYTHING is better than NOTHING! Personally, that little SIG 938 is about the smallest thing I leave home with.
Just pick damn pistol and adapt!!! All this discussion about size is just a waste of time. A fraction of an inch in ANY direction, i.e. SIG P320 vs HK VP9 vs Glock 19 vs Walther PPQ doesn't mean squat no matter HOW one is carrying (open, duty, concealed) since open/duty is already determined by the gear one has already selected (or that was chosen for them by the agency)! As for concealed, once the decision of WHAT to carry is made it becomes a matter of WHERE to carry. And now that fraction of an inch in handgun size doesn't mean squat either! Whether IWB or OWB, I seriously doubt that the carrier has a "special" set of concealment garments, one for IWB, another for OWB, or one for that SIG P320 and another for the HK VP9 and yet another for that Glock 19, since one STILL has to conceal that pesky grip sticking up!!! It has to be what is COMFORTABLE for each individual. BUT, most importantly, IT HAS TO BE ACCESSIBLE with minimal fumbling, contorting and grabbing shirttails or other garment parts. And BE CONSISTENT about carrying. Same place, same type holster, same type action, etc. Same for spare mags and other gear. Trying to remember where your knife or spare mag is at the least convenient time is muy malo!!!
Just an old fphart rambling on, but an EXPERIENCED old fphart. Experience - learning from non-fatal mistakes!