I think now days the mobile navigation also gives recalculation of route facility. One can use car charger for both mobile and GPS device. So battery usage time is not a problem. Other points are true and one has to pick depending on the priority. Another advantage with mobile is that they give better exchange price when go for a new mobile. I don't know there is any exchange price discount available for GPS device. 2-3K discount can easily get if mobile is in good working condition.