Where I live, Cops drive a variety of unmarked vehicles as well. From Dodge Durango's to Ford Explorers. Looking at headlights is pointless.
agencies also analyze what will be their workhorses. Cost, mpg, etc.
Durangos would be good in suburbia, terrible on interstates, wasting gas like a mofo sitting around. Explorers, better, as I believe that they are based on a car chassis now (I do not know).
V6 Chargers for in town, V8s for the highways.
But, you and others are right there are so many varieties in terms of the police switching things up.