Good GPS for Class A motorhome

I've used my phone as a GPS and it's ok, but there are lots of reasons why I still use a GPS which is designed specifically for that purpose. Too many to list here but it has a lot to do with POI's, accuracy, cell signal dependency and things of that nature that are inherent in a GPS which is designed solely for that function, vs a phone that was designed for a hundred functions. Size is also a consideration.