Harold got it right!
First, handguns for "operators", regardless of affiliation, are almost universally a last resort; long guns (your primary) rule. No one wants to use their secondary weapon, but in the extreme you want the piece of mind that you have one.
Second, "operators" get a lot more training/trigger time with primary and secondary weapons (or they dang well should!), so if they want a handgun that gives them more wood by making a bigger hole, then they can go for it.
Personally I am willing to entrust my life with the Beretta (since that's what the Corps gives me as a secondary) and the 9mm (which is what I personally use anyway). The 9mm is easy to shoot, gives you plenty of ammo, and stopping power is a myth. Make two holes in a sheet of paper, one .355, the other .45, then hold that up to your chest. Do you think it'll really make that big a difference? It certainly could, but .1 isn't worth the trade offs in my opinion.
Also, stories like, "I shot him 50 times in the chest with my 9 mil and he kept coming," versus, "I shot him in the left pinky finger with my 45 and he flew 50 ft across the parking lot," are b.s. They make for great stories, so have a beer and talk trash about "wimpy" handgun rounds; when you sober up come back to reality. Reality is this: all handgun rounds are weak, and the differences between the common fighting calibers (9/40/45) are practically speaking irrelevent.
That said, shoot what makes you happy; nothing else will do!