Topo maps show terrain detail. Rise and fall in elevation by the use of contour lines, creeks, swamps, and other features.
A road map doesn't show you the hill is tall, that the elevation changes 1000 feet in 500 feet of travel etc. How to Read Topo Maps http://www.maps-gps-info.com/topo-maps.html
Topo maps are what you want in a wilderness area.
You need to set the device to use the correct datum (a mathmatical formula that is used to determine the center of the earth and the projection of points on to a sphere to greatly over simply the term) (usually nad27, but each topo map references what datum was used to create the map).
Lat and Long have long been used but is very difficult to use in conjunction with a paper map. UTM or Universal Tranverse Mercator is a metric grid, very easy to use, and is accurate to within a few meters which is why a modified UTM system is used by the military and especially in artillery. Universal Transverse Mercator coordinate system - Wikipedia, the free encyclopedia
I have the entire SE, USGS, 1:24,000 quadangle topo maps installed on my gps but I still take a paper map which gives a better perspective as it's much larger than the small display on a gps. Also, if the batteries die, or the gps quits working I still have a map but have to rely on feature identification and cross referencing to determine my position using the map and compass.
Like anything else, the more you put into learning how to use it, the more you get out of it when you really, really, need it.
We ride a fair amount in the mountians of East Tennessee/N. Georgia which contains the Big Frog and Cohutta Wilderness areas. Combined these wilderness areas make it the largest wilderness area east of the Mississippi. Needless to say, it's very remote. Getting lost and not being aware of ones position can have unpleasant consequences.
Most days we ride we never meet another person and even on the more popular trails it's usually several hours between sighting other riders.
We love it because of that, but should something happen help isn't close by.