I am too much addicted to Google..So, my answer will Google..And whenever Google finish then i will go for other like Yahoo and that is like impossible..
Google is the best, they don't stop improve their services, all that with a simple and fast site, I like the quick search and "do you mean ...." notification, some times I feel that google know what I need before start using the keyborad.
Google has a strong local searches and we can't compare it with yahoo because google implement it according to google maps. you local business is verified with google maps. secondly, Google is the world most strong, huge and faster search engine and most widely used search engine. Gone the days, when people love to use yahoo email, messenger and also used as a search engine. Now a days, Google give you every thing in one plate but i say, more then everything. You have a strong gmail like email, you have maps, apps market, Android OS, search engine, internet docs, chrome like browsers and there are many to mentions. Due to the huge package and elegant functionality of Google services, people from all around the world come to Google.
I still use google because it does a pretty good job of knowing what I want when I type it in the search bar.
I prefer Google than Yahoo as it's the largest search engine. But it's all up to our own preferences that someone likes Yahoo and others Google. But i personally experienced that Google provides more information than Yahoo as well as other search engines.
I think Yahoo simply stopped looking for improvement. Google is an advanced company and search engine that has nothing to do with Yahoo!
google have search engine, have gmail have google map and many other apps yahoo have less apps then google but until today many people still use yahoo mail and yahoo messenger