Adsense has been known to trick us all. I did an experiment once for a one page domain. The statistics indicate 143 visits on one day. But google only saids 50. Either way google has dropped earning rates too. With more traffic i am earning only $100 a day. While I was earning $150 a day with less traffic before.
There are many possible reason that this may be happening. If you are using GA in an optimal way filters are used. E.g. - Block IP's that should not count as visitors like you and other IPs - The urchin code can track a returning visitor for up to 6 months, if they return by another medium the source code will be overwritten. Source - There is always discrepancies between AdWords and Analytics because of this. Also consider what GA does that basic server stats software doesn't do: - Conversion reporting - Goal Funnels - Custom filters with expressions - Focus on CPC only using manual tags IMO, when you learn advanced methodologies in GA it is very pure, accurate, customized reporting. To test concepts create multiple profiles and play with filters, you'll see the difference between profiles. **NOTE: data may take up to 24 hours to show in GA** I could go on and on but I spare you this time . Cheers, H
Guys I know I am too late but still I want to share one link which perfectly gives your answer with satisfaction. http://www.maxxor.com/blog/google-analytics-vs-awstats
Just You need to know what more important. Server statistic based on server log are much more usefull from each other using Javascript, because: #1 If somedody trying to hack your server or making high volume of queries for your website, its not visible by all JS based statistics. #2 Not everybody have switched on Javascript. #3 Sometimes single hit can be missed by connection problem.