Google is no doubt better, but I'd rather have thousands from Yahoo than just hundreds from Google. I prefer the one that brings more people in. That said, well, Google usually brings more people in, so agreed x2
To help rank better in Yahoo. 1. submit your site map to yahoo 2. submit you media content content via RSS 3.submit your RSS 4. make sure you allow yahoo robots to crawl your site in your robots.txt file