Very interesting study comparing search results of major legal databases.

Study concludes: "For results that return the largest number of more recent cases, researchers should turn to Casetext, Fastcase, and Westlaw. The highest percentage of relevant cases, as defined in this study, can be found in Lexis Advance and Westlaw. Google Scholar has the most older cases in its results. And Lexis Advance returns searches with the most results."

The Algorithm as a Human Artifact: Implications for Legal {Re}Search

Study by Susan Nevelow Mart (Director of the Law Library and Associate Professor at University of Colorado Law School).