currently, in my area and in my travels, as far as dept issued handguns, it would be
1. glock
2. sig
3. smith m&p
among officer purchased duty weapons
1. glock
2. springfield xd series
3. sig
in both groups, 40 cal is dominate by far.
just what i see....your observations may vary.
as far as playing copycat to officers/agencies in firearm selection, on one hand it is understood that the firearm model passed testing. It is also great free advertisment for a firearm company to have their model out there and visable to the public in the holsters of officers. I never liked the herd mentality and would rather choose a weapon/caliber best suited for my needs. Not a one size fits all handgun as in dept furnished. And officers choose private weapons based on many factors including quality, price, fit, or just plain wants.
I want a measure of control over my own destiny.