JEEP all day, these newer explorers are just terrible (esp from and enthusiast point of view!) my aunt had an 02 explorer, low ground clearance and just very blah, my pd has an 03 with 20k miles and all around just slugish, rough ride. my other depts just blew up with under 80k miles on it, neither are used for routine patrol either.
as far as jeeps... HEMI
i dont have that much experience in the year/body style u mention, but the 99-04's are fantastic even with high mileage