I believe most PD's in the US used the Springfield Armory in the recent past.
However, there seems to be a shift towards the Sig's and Ruger's as of late. My understanding is that they had to upgrade to "compete" with the criminal underworld that has out-gunned them for quiet some time now.
having said that, the Springfield Armory XD-40 ought to serve us,private citizens, well.
STICK WITH WHAT WORKS FOR YOU!