Provided you understand how to use your unit, you do not get much more out of any of them other than your position
(1) If you have no understanding of a GPS and just switch it on and leave it for a bit, it should show you your position (plus numeric data on track, speed etc).
(2) If you use a GPS properly, you load the planned route into it and it gives you guidance along the entire route, with numeric data on ETA etc.
To do (2) one can either load the waypoints manually (time consuming) or load them in from a flight planning program such as Navbox. The latter method eliminates all sorts of possible user errors, and since one also has the plog printed off the program, the route in the GPS matches the plog. Very handy, and very hard to make a gross error.