I'm a big fan of both maps & a GPS. The map gives a great overall view of the area, while the GPS will provide a smaller, but much more detailed view. Both can lead you astray - you have to add some common sense with either.
My favorite "bad map" story was a 1972 trip in July from NY to Leadville, CO. AAA made us a TripTik that routed us on Mosquito Pass Road between Alma & Leadville. On the map it looks like a good idea
. In reality, while called a county road, it is a jeep trail that goes over 13, 185' high pass that doesn't usually open until August. Our friends in Leadville gave us the proper route, and, on a later trip, took us to the pass in their Trooper; it is safe to say my 1969 Camero would not have liked the drive!