The thing I like about the Glocks is you can have a G-26 (10rd) and use a G-19 (15rd) mag or a G-18 (30 -33rd) mag. There is even a sleeve you can put on the 15rd mag to make it like a grip extensionon a G-26.
I just got a G-23, 15 shot, 40cal in a trade, and have had my G-19 for over 20 years. I may not keep the G-23, I already have a Kahr PM40, and the 23 is bigger than I want to carry.
John