What did I miss?
.40 vs. .45 is kind of a silly question, it just doesn't matter.
Department policy, selecting a handgun with the features you need, and ensuring it fits are far more critical than choosing between two calibers that have proven records.
Finally, and most critical, learn how to shoot it well and maintain proficiency.
With a quality bullet - Gold Dot, HydraShok, SXT, Golden Saber - the difference between .40 and .45 is nil. Pick the one you shoot the best.