I’m using another statistics plugin/service and get different numbers for them, why?

Pretty much every plugin/service is going to give you different results for visits and vistors, there are several reasons for this:

  • Web crawler detection
  • Detection method (javascript vs server side PHP)
  • Centralized exclusions

Services that use centralized databases, like Google Analytics, for spam and robot detection have better detection than WP Statistics can. The trade off of course is relaying on an external service.