Google vs. Yahoo! search?

Researchers at the National Center for Supercomputing Applications (NCSA) took up that question, and have now posted their study results: "A Comparision of the Size of the Yahoo! and Google Indices."

Snip from conclusion: Based on the data created from our sample searches, this study concludes that a user can expect, on average, to receive 166.9% more results using the Google search engine than the Yahoo! search engine. In fact, in the 10,012 test cases we ran, only in 3% of the cases (307) did Yahoo! return more results. In 96.6% of the cases (9,676) Google returned more results. In less than 1% of the cases (29) both search engines returned the same number of results.