Most department purchases (Fed and local) are run by the accounting area or firearms training officer bias (if his strings are better than accounting.)
Look at end users also. Different body shapes, sizes, and mind set all come into play.
The 40S&W came about because the 10mm was too "hard" for some FBI agents to handle.
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)