Conclusion: The Navigon-powered Delphi NAV300's feature set is almost identical to the Navigon 5100's. If you don't need the live traffic option but appreciate a Bluetooth phone interface, the NAV300 is a better choice. But if you need live traffic info and don't care so much about Bluetooth, the Navigon 5100 is $100 cheaper than the traffic-enabled NAV300.
Pros: Offers text to speech. Optional subscription-free traffic function. Multisegment routing. Zagat Survey listings.
Cons: Can't search POIs near destination or near specific address. Bluetooth phone interface doesn't sync your phone's contact list or call history. Separate traffic receiver and antenna.