Click and Clack, the Car Talk brothers advise against getting old police cars. Not because they’re punished but because the engines have been used for many hours without showing that much actual mileage. The cars sit a long time with the motor running, wearing out the engine even thought the the mileage will be low.
At one point, New York State had a law forbidding the “Police Interceptor” badge on the trunk lid of the newer CV police vehicles from being displayed on non-police vehicles.
Anything that is going to be a common model for a police car is going to have a massive parts infrastructure to back it. The larger the # of vehicles in service the larger the OEM parts allocations will be for supporting them, making it more likely that parts will be plentiful for many years as well as making more cost effective for 3rd parties to make parts when OEM stocks start to shrink/disappear.
My brother drove a dark-colored Crown Victoria for a while. Rather than people slowing down around, him, sometimes when he would slowly cruise through certain parking lots, groups of people all of a sudden seemed in a hurry to walk or drive away.
