In a Glock 21, I get 14 rounds. In a Glock 17, I get 18 rounds. Not that big a difference. I can see the difference in subcompacts, but if all I have is a subcompact, I'm not exactly figuring in jumping into the middle of a riot. Honestly, in most everyday situations, I probably left the autoloaders at home or in my car, and have a 5 or 6 shot J-frame in my pocket.
One of the things I like about the 45 is that I can still shoot the outdated rounds for a reasonable price and get good with it. I buy the 100 round boxes of Remington 45 ACP JHPs, and shoot them quite a bit. I know if I bought $1 a round 9mm, it may be pretty effective, but I wouldn't practice as much.