These two models are quite similar in almost all aspects, they both have Bluetooth support for handsfree calling, FM traffic receiver for up to date traffic alerts, all the essential travel tools including mp3 and audiobook playback, as well as the vibrant widescreen displays. The only difference between these two models is that the 680 is a model that features support for MSN direct, which is a subscription service that allows the user to access a wealth of info including gas prices, movie times, traffic conditions, weather, and so much more.
The Nuvi 670 is a high end model suited for the power user who wants the luxury of a widescreen and features that would make any trip the highest level of convenience in either North America and Europe.