I own 2 9mm pistols but they are just range pistols because they are dirt cheap to shoot and anyone can handle them, but when I hear something at night I grab my .45 to go walk around because I don't want to have to pull the trigger more than once to drop somebody, and some people on drugs can take a few shots from a 9mm. If you aren't a strong shooter though get a 9mm with a bunch of target rounds, and when you need to have it in defense have some hollow points ready.
Here's a picture I just took of my 3 different handgun rounds. 9mm, .45ACP, .44MAG