The DW (aka the navigator) thought her smart phone was just fine, but after two years of it she now wants a tablet with cell connection.
The phones are too small for detail. Then if you set them down for a moment and pick it back up, you always touch something, either a button or the screen that you shouldn't have and then it takes you several minutes to get back to the screen you want and meanwhile you've gone by a turn. It all gets much worse if the driver is trying to use a smart phone in traffic.
Buy something like the Garmin 760 with a large screen and mount it so the driver can see and listen to it if they want. Why create stress trying to use a phone as a GPS.
And a GPS for truck or MHs like the 760 will help keep you off of roads you might not want to be on with a large MH - single lane roads, small bridges, low overheads, weight restrictions, etc. A cell phone won't do that.
And using the phone as a GPS with Google maps drains the battery rather quickly.
Get a phone to talk on and do emails or texts, get a GPS if you want a GPS..........
Bill