We have had a Garmin RV760 GPS for about six months now. We had two previous Garmins and so familiar with the controls. I also have a 5" screen smart phone that gets google map directions.
In the six months we have been using the Garmin 760 it has not once misdirected me in the RV. It has a large easy to read screen. Very helpful is that it gives you the lane you should get in to when you need to turn or make any other maneuver. It also has voice command. We tow a Jeep Wrangler. I got the optional back up camera with the Garmin that I use in the Jeep. Works well. I like the new voice command on my phone that is called google now. You can tell it to find a place and it works very well now to look up what you tell it to and give you directions to. For an RV the Garmin is a far superior tool. It is MUCH more reliable. 95% of the time the Garmin functions perfectly. I would say the phone and google might be in the 50% range. With a car you can easily pull over and stop to correct, but you can't do that in a 40' DP. Plus the Garmin tailors the route for the size of your rig.