As we are talking about Ouray county's choice for some of their vehicles, I'd say that having been through San Juans, they made a good decision by adding the FJs to their fleet. Ouray is over 7,500 ft. and almost surrounded by steep mtns. Many of the paved roads are narrow and windy with lots of major changes in elevation and switchbacks. Also, as they are the Sheriffs of the 'Switzerland of America', they probably spend a lot of time on the rutted, rural, back country roads/trails, and much worse that would tear up a high speed pursuit vehicle. Reliability in these conditions is key. A large SUV could also prove to be impractical. They may experience conditions very different than the flat, straight highways or gently rolling hills like there are in say rural Kansas.
I am one of many volunteers with some of our county Sheriffs who use 4wd pickups and SUVs, as well as cars. They are called to assist in rescue and all kinds of situations where they must be self contained and handle some less than urban conditions in a very large county in WY. If they get near a highway or municipality and need a pursuit vehicle, they can call the HP or locals to assist or radio for one of their sedans to intercept where the paved road begins. It's hard to outrun a Motorola.