· Mantis Stats uses the webserver's log files. This gives it access to absolutely every visit to your website.
· Mantis Stats include search engine crawler visits from sites like Google, Yahoo, Bing, etc... (Google Analytics cannot)
· Many of your tech-savvy visitors will have blocked Google Analytics from loading. You cannot block Mantis Stats.
The Take Home
Use either (or both) to track trends, most visited pages etc... Armed with the above information, you can choose which to refer to in regards to traffic. There isn't a right or wrong, however we feel that the Mantis Stats are more accurate since they are generated from the raw webserver logs directly.
If you're looking to sell advertising space on your site, quote both sets of figures to prospective advertisers - or ask them which they would like.