How do you figure?
They both mark a waypoint and can take you to that waypoint.
The mapping one just shows you a topo map of the area as opposed to a plain field with a waypoint on it.
I have been using a non mapping GPS in my boat since 1995 and have no problem getting back on the spot.
Don't get me wrong I like my mapping handheld and want to replace my boat's GPS, but all the OP want's it for is to get back to his vehicle in white out conditions and a plain old basic GPS will do that and won't cost him $300. He does say he wants a mapping GPS, but for what he wants to do with it, it's not needed.