Catalyst Group have performed a study on Google vs Bing, the results came out with the majority of searchers preffering Bing’s Search Interface over that of Googles. Altough searchers preffered the Bing Interface, they still choose to stick to the search engine they are familar with, which ofcourse is Google. See below for the presentation, showcasing the results:

Catalyst Group Bing V. Google Usability Study