We have used the Rand RV/Truck GPS with free lifetime updates for almost 4 years now. In my unit I wouldn't want my GPS in the radio because it is a lower line-of-sight. Don't want to be looking down, then back up, then down again. With any RV GPS you can enter height, weight, length, gallons of propane carried, etc. It will always generally route you so that you stay legal and don't tear the air conditioners off the top of your rig.
I run a second GPS (non-RV) mounted on the dash in front of passenger seat also. It doesn't hurt to have a second pair of eyes looking for turns. I only use Google Maps or other I-phone apps when camped and planning routes, never for actual navigation.
Full Time in 2017 Newmar Ventana 4369
pulling a 24' enclosed (Mini Cooper/Harley/Kayak)
(traded 2014 Thor Challenger)
US Army 70-73 Retired LEO