Springfield XD's haven't been around as long as the Glock 17. The XD hasn't proven itself just yet but the Glock 17 and other 9mm's have been in service for a very long time. It's everyone to their own but I would rather have 10 mags each holding 17 rounds rather than less rounds of a heavier catridge. Honestly, with very good combat ammo the 9mm will expand bigger than the .45 cartridge.