From the fine folks at Kelsey (blog) on Hitwise data on Local:
Yet Hitwise says the following about local:
Visits to Yahoo! Local (local.yahoo.com) were 4.4 times greater than visits to Google Local (local.google.com) in July 2005. However, Google Localís market share increased 61 percent between February 2005 and July 2005, while Yahoo! Local grew 14 percent. Google Localís catch-up is occurring amidst the growth of Google Maps (maps.google.com), which has quickly grown to become the third ranked site in the Hitwise Travel Ė Maps category in July 2005. Maps have proved important to local search users, as 17 percent of Yahoo! Localís visitors went directly onto Yahoo! Maps in July 2005.
Google Local definitely feels like a better service overall - and I think it should eventually pass Yahoo Local.
For one, Google Maps technology is more responsive than what Yahoo is offering. You can be pretty sure that Yahoo engineers are working to catch up here, and integrate this kind of mapping technology with Yahoo Local.
But, I think the real long term differentiator between Google and Yahoo is how they source their local data.
Yahoo seems to rely on a top down approach, which imports data mainly from existing Yellow Pages listings databases, like infoUSA. OTH, Google is cooperating with webmasters, and organizing local data that it finds on search crawls.
There is just so much local data, which changes so frequently - I'm inclined to think that Google has the right approach here.
Looks like a mix of data sources. I'm not sure how priority is established. For instance, for a particular accountant in Pittsburgh PA, Google Local is finding 90 different references. These references include the SuperPages listing for this person, a website showing this persons CV, a trade website showing this persons speaking schedule, and a couple of other websites, where this person has contributed articles.