While it wasn't the focus of the recent Nielsen//NetRatings talks, I found it striking that the conversion rates generated from Google searches can be substantially lower than those coming from Yahoo!.
Anecodotally, Nielsen//NetRatings noted that while Google drove more visits than Yahoo! did to one mega-retailer, Yahoo! delivered better quality.
- 52% of the retailer's site visitors came from Google, compared to 28% from Yahoo!
- 45% of purchasers came from Yahoo!, compared to 42% from Google
Yahoo!'s searches drove more actual buyers. I would expect some variance in results from the different search service, user base, etc...but not this much of a variance. Nielsen shared this as an example of the nuances of search, and it shows that the nuances have a substantial impact.