The only real way to actually test out search engines. Compare the results with all of the formatting removed and location radomnized. Here’s a great site to test it out for yourself. You do a search and then vote for the site that you think has the best results.
In the early voting it looks like Bing is actually edging out Google by a slight margin. At the time of writing Bing is up 42% to Google’s 41% with Yahoo trailing behind at 17%. It’s often apparent that two of the results are quite good while the third is not nearly as good with the third place result being Yahoo.