Search engines and directories are completely different. Directories have rigid guidelines for sites and use "human indexing;" people review, based on quality functionality, contents and design of a site and index links before adding to their index. Site’s Webmaster strives to categorize sites as accurately as possible. So, directories have a smaller, but cleaner index. Search engines rankings are based on the %age that will be placed on keywords, meta-tags, title, link popularity etc. that might be irrelevant to directory rankings. Any search engine will use a combination of factors to devise its formula.