I lean towards using Google for my personal search. As far as traffic to my website, though, I am noticing that Yahoo! is gaining on Google. Currently 48% of my total traffic comes from Google and 27% from Yahoo. A year ago Yahoo! brought only 19%. So Yahoo! is gaining on Google in my search results. Yahoo! is also beating Google in pages/visit and average time on my website.
Accuracy is a subjective thing and I think there is really not much between Google and Yahoo. Yahoo however has been willing to do a bit more innovation ( I guess they have less to lose). For example they have added a new "Yahoo Search Assist feature" as a dynamic search guidence functionalities which I think is really cool. I blogged about it here for those of you interested - www.search1x.com/2008/05/03/why-you-should-try-yahoo-search
You can't compare Google with Yahoo. Google was made to be a search engine, it started out as a college project. Yahoo instead concentrates more on services.
Jim brings up a good point. Yahoo tends to bring higher quality traffic because the people who use Yahoo search tend to be older, as in 30+ years old. The teenagers and the younger generations all seem to use google now. Not only do the young people have no credit cards but they are more web savvy and less likely to click ads. I went to a SEO convention recently and the guy running it took a poll on who used which search engine more - google or yahoo. To my surprise, far more people used Yahoo. It makes sense now because the average age in the room was probably 40 or higher.
my websites are all in the top 3 positions on Yahoo, but i hardly receive if at all any leads or enquiries from yahoo, but when ever i put on Google i receive a high volume. yahoo may have a bigger database of sites but most important factor is that google generates the enquiries that a business needs.
lol .. my site is on top in yahoo results but a bit behind in google search for the same keyword ... but still google gets me with more traffic rather then yahoo or any other search engine .... yes Msn is better as a search engine then Yahoo .. i think so as per traffic to my sites and rankings