I find a lot of the time, Google makes a lot of the best and most accurate search results. Yahoo doesn't always have accurate search results. Its kinda like when you search for something and its not the most know thing in the world. I would search Google first, because of the selection and they get it perfect every time. Being with Google for so long, Yahoo's search engine and layout of the search profile is kind of a joke.
But hey that's my opinion, yahoo is a very well know search engine. I just trust Google more.
from my point of view there are two types of search engines the first one called search system and the another type called search engine
Google and yahoo are search systems , it means that they have their algorithm and the other search engines buy this algorithm from them but they put their details.
according to this i'm always prefer Google because it always change it's algorithm 😀