Ah the old favorite caliber debate raising it's head again.......

We can always invent scenarios where a hand cannon with large capacity of rounds is needed to stop the hoards of bad guys attacking.
In reality the average self defense shooting is against one person within 21 feet and only 2 or 3 shots are fired. The reason multiple offender and large number of rounds fired makes the news is that it was out of the ordinary. People who carry for self defense may get tired lugging a large capacity weapon around or have trouble concealing it so they stop carrying it. It's better to carry a comfortable weapon that you can hit the target reliably with then spray and pray.
When you look at history the .45ACP was developed for it's stopping power since the soldiers fighting the Morros in the Philippines were complaining that the standard issue .38 couldn't stop the charging enemy. When you look at one shot stops in police and other shootings you will always find the .45ACP at or very near the top of the chart.
The U.S. Military was interested in keeping the .45ACP in service but they had to look at ammo resupply issues and the rest of NATO was using the .9mm so that pushed the change to .9mm. The military also taught things like field of fire and spraying enough rounds down range to have something hit the enemy. (one reason for full auto fire) but after awhile controlled fire was considered a better tactic (One reason for 3 shot burst vs. full auto).
The military also doesn't worry about where each fired round goes since they don't have to worry like a police officer or a civilian about hitting innocent bystanders.
I personally would worry about hosing down a neighborhood or parking lot with 30 rounds or more. I know it's better to be tried by twelve then carried by 6 but you better have some good legal defense in a shooting.
Police departments select weapons for many different reasons which may not translate for individual personal carry. Many departments standardize and require all officers to carry the same gun regardless of assignment (unless undercover) and sometimes even off-duty so they make compromises so that it works in uniform and off-duty as well as for large officers and petite ones. Sometimes departments resist moving to a larger caliber because they feel their smaller officers can't handle the size of the weapon or it's recoil. Sometimes selections of weapons are made based on contracts with a certain manufacturer or distributor not because of officer input.
I would also encourage a person who carries for self defense to try and stay with one caliber and style of gun in the same location of carry so it becomes second nature and you don't have to be concerned about mechanics of draw and fire and you won't have to worry about different weapon functions and ballistics.