I bought a Garmin DriveSmart 50 since the models I want are out of stock. It is very slow and at the intersection, it gave me the wrong direction. For example, it was supposed to tell me to turn left but it told me to turn right. I read that a gps is good in areas that cellular signals are not available. In big city, is that a problem? Google Map/IOS Map seem to be faster and more responsive.