I participated in a blind test between Google, Bing and Yahoo in my Information Retrieval class at a university, back in 2013. The results were: 1) Google, 2) Bing, 3) Yahoo - for every standard IR metric we thought of, which included NDCG@{1, 5, 10}, MRR, MAP.
Did the results get published? Were the queries "external" or "user generated"? We found it very informative to compare the results of relevance testers (which were people who were shown a query and a set of results) with users (which were people who actually generated the query and evaluated the results). I had hoped to get a study done to get more data on that.
