Exactly, search engines most often yields different results for the same thing, Yahoo quite often gives useless results. On the contrary Google gives pretty impressive results for the same search.
Yes, i think every search engine have got their own way out to search the results and i personally prefer Google and whenever i think the results are reliaible , then i switch over to Yahoo.
Every search engine have different results because they use different algorithm. There is no point in comparing the search results of two completely different search engines.