I have the Garmin 760 and it has been anything but a bowl of cherries. Froze in downtown Phoenix, numerous poor directions, improper speed limits displayed, directions to dirt road even though that option is not selected. Updated software/firmware which may have helped-but still occasional faulty directions. Such as telling me to turn right onto Pacific Coast Highway when I'm already on Pacific Coast Highway -and the right turn street has another name.
I have a smaller Garmin I use in my car and it has been fine..
I'm considering a second GPS, maybe Tom Tom, and running them both in the RV at the same time-choosing the directions which make the most sense. Or maybe just study a map more :)
I too like the smartphone google maps gps. But they're at the mercy of a signal.