Well if you want all those calibers than make a patch that adds them. :D 9x19mm Parabellum is the standard (and most common) caliber for the P320 unless you get a conversion kit for it or buy it in a different caliber. That's why it's 9mm and not 10mm for this one. Pages 1...
Another consideration is cost. The P226 costs $1087 MSRP for the base model; the premium models cost almost $500 more. The P320, however, starts at $679 for the base model full-size; you can get the full-size gun and a conversion kit for a smaller frame size for the same amount as...