Safari - Google loves it Yahoo hates it.
Google loves Safari and Safari loves google. But google changes lovers too often for comfort. On the other hand, Safari is head over heals. So she is going to end up heartbroken. The big brother is the default search engine for the Safari browser on OS X. Safari is so loyal that the search box in the tool bar has just the one search engine. It cannot be changed without resorting to hexedit.
Yahoo on the other hand hates Safari. It's more accurate to say yahoo hates OS X all together. Yahoo chat for example is not available for OS X, Hey wait a second gtalk isn't available either but ichat supports jabber, so that means you can use it with GTalk.
The new Yahoo mail sounds very exicting, it probably is exciting too but not if you are a Safari (or even a Camino) fan. So what's the solution? set your default search engine in OS X to be firefox.