I'm a TomTom fan, but don't use my phone for the traffic thing. I much prefer a dedicated device, I've used my phone for nav in a pinch, but it just not the same - screen too small, calls make the map go away just at the wrong instant, etc. etc. It definitely drains the battery faster - I try to make sure it's plugged in when doing nav so I don't have to worry about running out of juice later. I use it as a hotspot for my tablet to do customer invoices & etc.
That said, I do love looking up a contact and pressing the navigate icon to plot the route - it would be nice to have a dedicated gps that would sync with my contacts somehow.
TomToms (along with everything else, I suspect) have really gone down in quality over the years. I think I'm on my 5th one now, it's only 14 months old and already starting to go. The digitizer thinks the screen was pressed at random times so it goes back to the menu. Tried removing the bezel and cleaning the edge, but that didn't help, so it's already time for a new one. These 55-year-old eyes really appreciate the 6" screen, I'd get a 7 if I could.
Sorry, just rambling and didn't really answer your questions!