Having used all the phone based GPS systems, from Waze to Google maps etc, in the end I ditched them all out of sheer frustration and purchased a Tom Tom Go 60 and have never been happier. it really is a night and day difference, vastly superior forward warning of where to turn off, satellite signal sensitivity ( especially when its cloudy ) in heavily built up areas crowded by high rises, the dedicated Tom Tom GPS just blows all the phone based GPS systems AWAY !
Having used our Tom Tom in Europe, various parts of Asia, Australia and the USA, the extra money invested in high quality maps and such an easy intuitive GUI just makes driving so much nicer/safer.
My experienced opinion, pay the extra money and buy a dedicated GPS for the car, $1600 - $2600hkd ( with maps ) very well spent, Tom Tom really do produce an excellent product, that isn't limited by a smart phones weak GPS sensitivity and having a larger screen and much louder speaker, helps greatly...