A woman who wounds a would-be attacker will get more sympathy in a lawsuit than a man.
A 250lb man being injured by a .380 carried by a 110lb woman is not the same as a 250lb man being wounded by another 250lb man.
The military has moved away from the standard 20 caliber or 7.62 NATO round in favor of the 223 cal. M16 because of the higher rate of fire, as well as the lighter weapon am ammo loads.
Not entirely true. With the 5.56 NATO round (almost the same thing as the .223), the round and the tactics were designed to be that if you wounded an enemy soldier, it would take (3) out of action (the wounded, and two to carry him off). Remember, this was developed during the Cold War during the 50's and 60's when the threat was the Russians.
Now, you have Achmed who wants his 70 virgins, along with Rasheed and John (gotta be politically correct, right?) who want their vigins as well and don't give a rats hiney about Achmed.
Yes, you can carry a lot more 5.56 than 7.62 (the 7.62 NATO round is a short .30-06) but it takes on average 2-3 more shots to put an attacker down according to the stats that I have been reading. The rate of fire is statistically insignificant between the M16/M4 and the FAL or G3 (or similar .308 battle rifle) as very rarely do any of these rifles get used on full-auto for a full magazine, they are typically on 3-round or 5-round bursts.
Its all about fire-power not stopping power. Many police forces are moving away from the 5-6 shot 38s and 357s to 9mm, 10-12+ shot Sig Saurs, Glocks, Berrettas, etc.
In the case of police, yes, increased firepower, but also with advances in ammunition, commonality with different organizations, etc. It's also not always about projectile weight. A large, slow projectile and a small, fasty projectile can have the same impact. Force = Mass x Velocity. With frangible or self-protection ammo, size can be mitigated.
There's little than can compare to a .45ACP, but it's a heavy round and a heavier firearm. Few Men can carry one effectively in a CCW or Police situation, and far fewer woman can. Anyone who carries needs to be comfortable with the firearm so if that means a 250lb man carries a .22LR, so be it.