Google Battle measures which of two terms has a higher Google rating by searching for term1 OR term2 and then counting the hits of either in the returned top 100.
The current implementation only searches the snippets returned by Google; otherwise the whole thing would take a lot more time.
There are a number of implementations out there that just show you the number of 'hits' each term has and declares the one with the most the winner. It think the OR approach makes more sense; by asking Google to provide us with a list that contains either keyword, Google with indirectly decide which keyword it thinks is more important. Therefore counting the number of occurances of the keywords in the resulting snippets makes sense. The number of hits of a term doesn't mean much; I can create a million pages with my name on it, but that doesn't make me as important as Paul McCartney (oh well, he has 2 million anyway).