Yahoo! is the Microsoft of search engines. Bloated and aesthetically unappealing. The main Yahoo! page is an ugly jumble of tiny text, the result of a company that clearly has no idea what to do since it is just too big.
Google, on the other hand, is the Apple of search engines. Clean and simple, focusing on getting the results to the customers instead of trying to sell to them in any way possible. The main Google page shows just that - they are focused on their customers, not their money.
It's your choice
irmongoose