Hmm... for my own purposes, I actually prefer yahoo.. I pay less per click, my main products have a 1 in 6 conversion on yahoo, which they don't even come close to on google. So all you google lovers, just stay there and never mind what I said about yahoo!
I must admit, google search marketing has more user-friendly options.
As for yahoo having all the dating and shopping etc.. well, maybe that's why I do better there, I dont promote make money from home.
Ask me how to take an ebook away from the customer that got a refund.