Garmin is the standard others go by. The 660 and 760 have a ton of related RV data, and the price is reasonable. Voice is so so, but does work without needing to touch the GPS, I think sitting and learning where in the unit makes the voice more usable. But is nice to just ask where the next rest stop is or nearest RV park or fuel and then say go there. Cells are OK and have about the latest maps, I use both if not driving. the phone has one very nice feature and that is giving an alternate route when traffic jams up. But you need to kinda know the route with an RV so as not to get in trouble. And as above you need cell coverage unless you down load a mapping program of some sort and can do with a small screen. I have several Garmin's as well as the phone but for the RV it's the RV760 for size screen and added data.
LEN