Marketing needs the help of search engine more than anything else. After Google I consider yahoo search engine.Both Google and Yahoo are good search engine but Google is considered more than yahoo because you will get more traffic through Google.
There is no comparison of Google,if you will talk about search engine. Getting ranking on top 20 on Google is better than getting top 10 on Yahoo. Because Google has more search users as compared to Yahoo, almost more than thrice.
Wow.. altavista... I used to use that a lot as alternative to Yahoo. Back in the day, search engines used to be so much more predictable and static. Nowadays, the same search string can end up with different results in a matter of seconds.
I will say that there is no comparison between these two if you get top 10 in them, because it means that you will get visible on the first page and that's enough. Getting top 10 on Google is also having the equal importance as like getting rank 1 on Yahoo, reason is the same that you will become visible on the first page.