Navigon is better. TomTom offers nothing but a higher price.
Completely agree.
I own both, and I will be sticking with Navigon only for now to save some space on my 8 GB phone.
The RealityView Pro and Lane Assist functions of Navigon (as well as the nice $30 price differential) is absolutely enough to win me over.
If you do a Google search of TomTom and Navigon, there's a recent article somewhere (forgot by whom) with Navigon stating that text-to-speech is coming in their next update, and that they are definitely looking at eventually adding real-time traffic as well in the near future.
As it stands right now, Navigon has a much better feature set, price and, IMHO, I prefer the UI of Navigon's to TomTom's.
This bodes well for us consumers, as I fully expect them both to compete amongst each other until eventually, they are on par with each other in terms of price and performance. One thing I caution folks is not to take the 'TomTom' name too seriously when considering your purchase, as both Navigon and TomTom are well respected in the SATNAV industry, despite TomTom's edge in brand name popularity.
EDIT: currently, my biggest gripe with Navigon is its failure to list step-by-step route directions (a la Google Maps app). TomTom has this feature, and it's mind boggling why Navigon doesn't have it considering that they have far more sophisticated features implemented but left out such an integral aspect of a TBT app.
My biggest gripe with TomTom was, even in the middle of downtown San Francisco, the map would 'jump,' not accurately portraying where my current position was, as well as re-calculating the route unnecessarily. Extremely annoying, and I don't remember a single instance with which Navigon did that while I was driving. Also, there is an inherently noticeable lag with TomTom based on your relative position; Navigon actually maintains your current position fairly accurately, as I believe they may actually push your location slightly ahead of the map in accordance to your speed/heading, thus keeping your current position almost 100% accurate to where you actually are on the road....and, NO HIGHWAY VOICE PROMPTS! Navigon will say, "Keep to the left onto I-80 West" for instance, while TomTom just says, "Turn Left." Lame.
As an owner of both, in their current states, Navigon wins; TomTom came late to the party, relying primarily on their popularity to justify their price, instead of actually providing more feature sets than other satnav apps that are currently out. I'll give them the benefit of the doubt to greatly improve their app over time, but right now, it is extremely difficult for me to recommend TomTom over Navigon.