I dont know many cops who are gun guys to be honest. They just shoot what they are issued. once you start looking into it more you'll find alot of stuff out there that just doesnt make it any better than the 40 at a higher cost to shoot. keep in mind you'll hear one person say it sucks and then another say its the best thing since sliced bread too.
Heres another thing to look at. If the Shit really does hit the fan and you are scrounging for ammo, what are you more likely to find. 9 40 and 45 or 357 sig etc. if you want a 357 sig by all means enjoy it. Ive got a 10mm just because i wanted it