IIRC when dealing with non-uniformed combatants it was determined they could use hollowpoints. Which helps the 9mm, as well as the .45.
For a general issue pistol/sidearm a 9mm is somewhat easier to shoot and learn, especially for women. For the serious badasses, let their units pick what's best for the mission, be it a Grock, 1911, or whatever. I'm personally pleased with the H&K P30LS in 9mm; it seems the best of the plastic pistols, to me. Of course, it's also the most expensive of the plastic pistols
