We created jux2 as a comparative research tool to answer these questions. Using jux2, we learned that search engines are more different than people think, typically sharing fewer than 3.5 of their top 10 results (see the other statistical data). We also found that a comparative tool like jux2 gives users far more control over their searches and, in many cases, better search results than from any single search engine.
Jux2 runs your query simultaneously on Google, Yahoo and/or Ask Jeeves. Unlike meta search engines, which either aggregate results by source or post-process results with additional relevance filtering, Jux2 shows you which results are common or unique to each of the engines. A "What am I Missing" button shows you exactly what results appear in the top ten of Yahoo but not Google, or in Ask Jeeves but not Yahoo or Google.