Personally, I don't believe the FBI report that the 9mm is just as effective as the 40 and 45's. They will say that modern bullet designs have improved the 9mm's, but that same technology also improved 40 and 45's. I believe the main reason they went back to 9's, was because smaller agents; whether it be a female or small statured males had trouble qualifying with the 40's. So the justification was; well, the 9's are just as good. They also said that 40's were hard on guns and ammo cost is higher than 9's....Okay, that may be somewhat true, but look at the increased performance with the 40's. One caliber that I personally think is an underrated, and often dismissed is the 357 Sig. Lots of energy with superior temporary wound cavity damage and a heck of a wallop. A final note on 40's; you have a wide variety of bullet weights; 180, 165, 155, 135 grains at warp speeds and lots of energy. So, INHO caliber, and energy does matter.