Compare Google Navigation on Android, to TomTom on iOS. Navigation is free, works perfectly, and even goes so far as to include a "Car Mode" for docking your phone in your car.
TomTom costs, at last check, $95NZD. I've not bothered trying it.
I think the difference would be that TomTom supplies it's own maps in the App, whereas Google Navigation probably downloads the tiles/street view as you go.
This can make a world of difference when travelling abroad when you can't be bothered getting a local data plan.
I definitely use GPS navigation more often when travelling than when in my home country.
TomTom costs, at last check, $95NZD. I've not bothered trying it.