When i took my LTC class in Texas, the guy was a retired Captain of the LAPD. Served back in the 70's and 80's when LA was at it's worst. He used to tell us stories of the armed robberies and kidnappings that took place by the gang members. The average number of "armed" assailants in a "violent" crime was 3.
Think about that with your 9mm pistol and limited mag capacity.
Like someone said it's not like the movies, unless you are a perfect shot, you aren't stopping 3 grown men with 10 rounds.
This is why i prefer the 12 gauge with buckshot. I can fire off 5 rounds and reload 5 more in 20 seconds. I have two fully loaded Beretta shotty's in my closet, ready to go. No plugs, no fucks given.