Tough debate, everyone has good points. I went through this with my HD firearm and chose the 9mm for allot reasons. My Dept. just went with 40S&W, but everyone around us is going to 45acp. I like the 40S&W, it's a good round. The 45acp is excellent but expensive to shoot and sometimes the grip is a tad large. Paul Howe recently commented on Dept.s going to 45acp and the officers not being able to shoot them well when they show up for his courses. Good luck with your purchase.
Quick note on reloads. The only case I know of is a Hampton NH officer that used reloads for duty and it came up hard on him during the civil case, (he blew the suspect's jaw off during a confrontation.) The tort lawyer had a field day with him about using more deadly ammo that he had to whip up in his basement.