The only blind study[1] I've heard of on the subject put Bing ahead of Google at almost 2-to-1 (yes, seriously).
>> Conducted by California-based Answers Research, the study queried an online sample of nearly 1,000 people at least 18 years old, all living in the US. None of the participants in the survey knew Microsoft was involved. Participants performed 10 searches of their own choosing, and were shown the results from both Bing and Google, side by side, with all the the branding removed. Additionally, notes Microsoft, “The test did not include ads or content in other parts of the page such as Bing’s Snapshot and Social Search panes and Google’s Knowledge Graph.” For each search, participants chose which side showed better results, or could call it a tie. Of the participants surveyed, 57.4 percent chose Bing more often, 30.2 percent chose Google more often, and 12.4 percent didn’t prefer one over the other.
It was this study that inspired Microsoft's Bing it On campaign in 2012. Unfortunately, the ad campaign mostly consisted of Microsoft recreating the independent study, but cheating to make sure Bing would win even bigger[2].
>> Conducted by California-based Answers Research, the study queried an online sample of nearly 1,000 people at least 18 years old, all living in the US. None of the participants in the survey knew Microsoft was involved. Participants performed 10 searches of their own choosing, and were shown the results from both Bing and Google, side by side, with all the the branding removed. Additionally, notes Microsoft, “The test did not include ads or content in other parts of the page such as Bing’s Snapshot and Social Search panes and Google’s Knowledge Graph.” For each search, participants chose which side showed better results, or could call it a tie. Of the participants surveyed, 57.4 percent chose Bing more often, 30.2 percent chose Google more often, and 12.4 percent didn’t prefer one over the other.
It was this study that inspired Microsoft's Bing it On campaign in 2012. Unfortunately, the ad campaign mostly consisted of Microsoft recreating the independent study, but cheating to make sure Bing would win even bigger[2].
1) http://www.seochat.com/c/a/msn-optimization-help/microsoft-s...
2) http://www.435digital.com/blog/2012/10/09/bing-it-down-a-not...