Google Analytics only reports users with javascript enabled that don't filter google analytics with tools like noscript. It uses that and a user cookie to identify visitors and connect visits. This automatically processes out webrobots (like search engine crawlers).
Urchin analyzes your logs and uses heuristics (in layman's terms, guesses) to try to extract concepts like page views, visits and visitors. It identifies some webrobots, but fails in filtering them all out.
So, while reality is probably between those numbers, my experience tells me that Analytics is closer to the truth.
Google Analytics only reports users with javascript enabled that don't filter google analytics with tools like noscript. It uses that and a user cookie to identify visitors and connect visits. This automatically processes out webrobots (like search engine crawlers).
Urchin analyzes your logs and uses heuristics (in layman's terms, guesses) to try to extract concepts like page views, visits and visitors. It identifies some webrobots, but fails in filtering them all out.
So, while reality is probably between those numbers, my experience tells me that Analytics is closer to the truth.
Best of luck,
João Miguel Neves
Compare what GA and Urchin report against your webserver access logs. Then you'll have some idea of how much traffic actually hit your server.