Good short summary of how search engines spiders perform across all the major search engines to include Google, Yahoo, MSN, and Ask. Google far out performs all the other search engines in picking up new content. The article does not address relevancy which Google does well. Personally I think Ask does not index pages as fast or in quantity, but some how it does well in picking very relevant search results for most search queries.
Digg.com posts, “It (Google) simply crawls faster and smarter. Post compares how the other ones do”