The great caliber debate is more of a myth than anything. What you shoot well with is the best caliber for you. But, now we have a whole slew of fantastic scientific evidence from the FBI ballistic labs that helps solidify and justify their recent move to the 9mm caliber.
Earlier this year is when the FBI announced their return to the 9mm after finding that 40S&W rounds were causing too much excessive wear to their firearms.
First reported by looserounds.com, this justification below is worth the read. It may change your mind once and for all, and change what you think you may know about the 9mm cartridge.