Can’t see how it’s easier.
I don’t have to buy a second device.
It works exactly the same as a standalone satnav.
I’m never without my phone whichever vehicle I happen to be in.
It charges my phone while I’m driving.
I don’t have to leave anything in the car to get stolen.
You get a phone call, it interrupts the nav and doesn’t always go back to the app afterwards automatically.
Screen is too shiny on a phone, standalone devices generally have an anti-glare finish.
If the app crashes or goes off the screen for any reason, you have to fiddle around the phone’s menu to relaunch it (as opposed to holding power-off/power-on to reboot a crashed tomtom)
If for any reason your phone wont charge, you lose both your satnav and phone.