Shawn Campbell of Search Engine Guide has written a comparison on Yahoo Search Marketing vs. Google AdWords, covering topics like bidding, low click-through rate dropping, showing ads by country and language, reporting, keyphrase comparison, and conversion of three ad campaigns.

The test shows that Google Adwords has higher conversion rates than Yahoo Search Marketing. I doubt this will always be the case until I see more data.

For now, you can get lower cost per click for the same position in Yahoo. Google does reward advertisers for better conversion and take that number into the formulae to determine position/ rank. This advantage by itself is enough to get lower price per click if you know how to get better click-through from AdWords.

Read the entire article at Search Engine Guide.