9mm gets no respect...why?
It gets plenty of respect. Just not in the U.S.
In the U.S. the gun community has been brainwashed by decades of propaganda, mostly from gunwriters, asserting that any caliber that doesn't start with a '4' is ineffective.
Pistol wise I believe it is the second smallest round next to a .22...
There are a number of pistol calibers smaller than the 9mm but larger than the .22. The .25ACP and the .32ACP are a couple of the most common.
Idk, a .45 is just scarier mentally imo.
Spoken like a true "student of science"...
Before adopting the .45ACP as standard, the US Army performed extensive tests on cattle and human cadavers. Where a magazine full of 9mm cartridges failed to effectively put down a cow, two or three shots from a .45ACP would.
The tests did not involve the .45ACP for the simple reason that it didn't exist in 1904 when the tests were performed. Second, the tests were not "extensive" in any sense of the word, they lasted a couple of days and involved shooting only about a dozen animals.
Finally, the live animal testing didn't provide any results nearly as definitive as your post implies. The live animal testing was very loosely controlled involving a variety of animals (in terms of size) and variable shot placement, variable numbers of shots, etc. which resulted in outcomes that couldn't be correlated to ammunition performance in any useful manner.
In the first day of live animal testing, the .30 Luger outperformed all the other tested ammunition by a large margin, killing the animal with a single shot through the lungs in only 30 seconds. None of the other rounds in the first day of testing killed the animal in under 2 minutes from the first shot in spite of the fact that all the other rounds tested involved shooting the animal at least twice. The second day of live testing (in which they completely changed the testing methodology due to the fact that the testers were not happy with the first day's results) yielded equally variable results and they ended up shooting hanging cadavers and selecting the bullets that made the cadavers swing the most. In other words they selected primarily for maximum momentum. The kicker is that they didn't even measure the swing distance, but rather scored the sway subjectively. As in: "Oh, that looks like a 100." or "That's only an 87.", etc.
http://www.sightm1911.com/lib/history/background.htm#test