Yahoo has good search engine but there are too many things on the display or choices in the both search and messenger. google on the other hand has more simplified view which seems more orgnized and clutter free.
I agree with zzgear, Yahoo used to be better than Google. Back until 2005, I still think they delivered less spammy results, it was also easier to SEO yourself to high results, especially if you had a Yahoo Directory listing... But then around 2005-2011 they got extremely popular with Messenger. In that interval of time I think more people used Yahoo Messenger than ever before or after... at least from what I could see. Despite the fact that they launched Messenger in 1998, it got far more popular after 2005. Since 2010-2011 they started losing ground to Skype, but then Facebook. Eventually I think Yahoo Messenger will drop if they don't invent anything new again! Yahoo should go more into social media-social search-telecom and they might have a chance to cope with both Google and Facebook. What if they created a Google-Facebook type hybrid? "Goobook", "Fagle" (joke)... They will have to change their business model in order to advance and cope with the threats.
Yahoo is Famous for messenger and most people use the messenger than search engine because Google has the best search engine.
I think there is no comparison between Google and yahoo from search engine point of view. Google is a giant in search engine mechanism while the Yahoo can't compete Google in the current scenario. As for the Yahoo Messenger then it has an edge on Google. Yahoo has a great messenger and a lot of people around the world was definitely loving it. They has superb chat-rooms and etc. But when the Microsoft purchase yahoo then it stop the chat rooms and other different services. On the current time, yahoo messenger popularity is low if you compare it with other competitors of the market.
As a product Yahoo is always remembered for Yahoo answers, Flickr, messenger, News etc. Yahoo is very good as a messenger, but not that good as a search engine. Google provides the best authenticate and validate SERP's and is the best Search Engine ever.
Google is the best and you will get what you are looking for. Yahoo has done all wrong when it comes to search domain
I were using yahoo just because of their messenger. And i can say that i'm quite satisfied. I like that you don't even need to open your mail, to check if there is new mail. Talking about yahoo as a search engine, i can not say much. Google is irreplaceable.
As discussed below yahoo is mostly used for messenger but in case of search engine google is best for searching