I guess it depends on what you compare them to. Compared to Manhattan or southern Westchester County, Dutchess and Putnam counties are more rural on the average. (As for Orange County, I have no idea.) Compared to northwestern South Dakota, all these counties are suburban, even the least developed parts. You never see "next gas 58 miles" signs, for example.
Much (or all) of Dutchess county is engulfed by suburban sprawl, especialy the southwestern part.