You cannot compare yourself with truck owners if you are planning to travel in an RV, since they are routinely on the highway and know the routes very well. But you as an occasional traveler in an RV, will face great difficulty in finding your way in the new regions. So you can rely on a GPS system that comes with a range of RV specific features.
You may decide to use your car GPS in your RV, but this will not work for you. The reason is the size and built of the RVs. They are longer, have higher elevation and are much heavier than a car. The GPS, which is installed in your car is specifically designed and created for a smaller vehicle and has the speed and size limits as well. If you try to use them in the RV, you may stick in some difficult situations or places which may leave you in some grave problem.
You have a higher risk of getting into some troubles like arriving on a road that is meant only for small cars, pass through a bridge that is not suitable to bear the weight of an RV or being guided towards an overpass for which your RV is too high. This can be a real difficult position as you may be stopped or issued a ticket by the highway traffic cops for posing a danger to other drivers.
GPS companies have observed this need of RV travelers and are trying to tap huge profits by designing special RV GPS devices to provide updated, accurate and quick location information through a reliable and exact navigational system. The GPS industry has been very successful with the car GPS and the innovation and research being done is sure to give some perfect GPS device for our next vacation.