And, energy delivered = bullet mass x velocity. In many of those comparisons, the 9mm actually wins. That's why many LE organizations have gone back to the 9mm. More shots = more effective threat deterrent, at lower cost.
Hold on now. Up here in the northeast its primarily .40 or 45. While duty weapons for L.E. are high capacity SHOT PLACEMENT is the main concern, I.E. center mass. Unlike the bad guys the good guys have to account for every round, no "spray and pray". To my knowledge none of the agencies in my area have gone back to 9mm, in fact some are going from .40 to .45. Either round is still effective, especially with some of the loads now available.