I've used the navigation options in 2010+ models of cars from Audi, Nissan, and Ford and I can say without a doubt the TomTom is my favorite. The Audi looked nice and especially recently has some cool new features such as 3D cities but TomTom's unit was the fastest in responding, easiest to enter information with its touch screen (Audi's MMI makes it very tedious to enter information), and has maps that looks nice and crisp and the display shows lots of useful details.
When I switched from the Audi to the CX-5 I assumed the TomTom wasn't going to be anything special, and it's not, but it's really good and it works and looks just as good, if not better, than what else is on the market for factory built-in nav.