The biggest reason why the difference in numbers can be way off between counting visitors with the WP Statistics plugin and counting visitors through Google Analytics is because of how these two different tools are coded into the back end of your website.

Some guests (or more likely, some robots) are accessing your website without processing Javascript and when the Javascript doesn’t get processed, tools like Google Analytics will not record their count. Quite a few users today have some sort of “ad blocker” installed on their browsers which means they do not execute any Javascript when they visit your site, so Google Analytics isn’t actually able to track these visits.

Another small thing to mention is that WP Statistics is updated a few different times throughout the daytime, while Google Analytics is updated after midnight and only once per day. So, try not to compare data between these two tools for the last 24 hours as it’s likely going to change.