TechCrunch has an outstanding review of mapping services offered by Yahoo, Google, MapQuest, Ask.com and MSN. The review takes you through scoring on views, navigation, mapping routes, functional actions and services and pricing. Overall, Yahoo maps wins over the other mapping services.
Yahoo Maps was by far the best application tested. Its fast Flash interface, multipoint directions, live traffic information, and easy send-to-mobile feature make it the hands down winner. It also features the most robust API options.