I'm more interested in the overall quality and reliability than how many rounds a firearm may hold. I do own a Springfield Armory XDM 9mm with the 19 round magazine. The XDM 9 is a very well made and reliable gun. Its 19 round capacity peeked my interest, but was not a deciding factor in making the purchase. A good friend had allowed me to shoot his XDM 9 at the range, and I was sold. Went out and bought one the next day.
Springfield Armory is coming out with an XDS 9mm version; a slim, single stack, concealed carry version, that holds 7 rounds. I probably will get one of those eventually too.