I've shot steel cased 9mm through a glock 17 as well as steel cased 7.62x54r.

​​​Brass is much easier to reload.

Cost.

Brass in my experience typically seems to run cleaner.

People think that steel adds wear to the firearm. They're probably right. But many people will never shoot enough to know.

I've ran many many thousands of steel cased 9mms through my Glock. And it still runs like the day it was new.

I'll continue to buy whatever is cheap and continue to practice often. Glocks are cheap anyway, when it's time to get a new one, that's not going to break the bank.

-Jake