"Nonetheless, if I was in a department that issued .40 or was doing a lot of LE work around vehicles, I'd be strongly tempted to carry a M&P40. Lots of 180 gr JHP's that do well against intermediate barriers is a good thing." -- Doc GKR on 08-29-14
I currently work part time as a patrol officer for two different agencies. At one place (the department I retired from) I am issued a Gen IV Glock 22 with a Streamlight TLR-1 WML. (Winchester Ranger issued for duty ammo) At the other agency (where I've worked part-time since I was in the police academy[which was 1981]) I carry a personally owned Gen IV G35. (Hornady Critical Defense currently issued for duty ammo)
I am about to begin learning how to run an RDS on a handgun (Trijicon RMR06 type 2) and might? eventually use an RDS equipped handgun on duty. I'm a big boy and shoot full size .40 cal handguns just fine. If I do transition to an RDS equipped gun (at least part of the time) I'm wondering if I should stick with .40 S&W or go back to 9mmP. (I am partial to the G34/G35 pistols)
I live in Wisconsin, and penetration of heavy winter clothing would be an important consideration about four months out of the year.