A few things that could be contributing that you could look at...
If you have enabled IP subnet exclusions you could be excluding more visitors than you intend from the statistics in WP. If you are trying to exclude a single IP address then you need to make sure to include a subnet mask of 32 otherwise the default subnet mask of 0 will be used.
Verify Google Analytics Only Appears Once
This may sound simple but it happens frequently, especially when using CMS's like WordPress, that the Google Analytics code winds up appearing multiple times on the same page which causes multiple hits on GA servers for each page view. Check this using your browsers
view source tool and check over to verify that the analytics code is only called once and is only pushing the pageview event once.
Check Server Error Logs
Check your server error logs for one of the sample days and see if there are any errors with messages coming from your WordPress installation. Due to the way exceptions are handled within WordPress at times a plugin can fail in a certain task but still output the page to the browser as if nothing is wrong. If this is happening then it is very possible that WP Stats is not loading the data into your database for the visit but is not preventing WP from generating the page and sending it to the end user.
Dig Into the GA Records
Take a very close look at your Google Analytics records and check information such as browsers, geolocation, and if a visit has been flagged as a search engine or not. Even if you are comparing what has been considered
organic unique visitors daily it may be flagging differently between the two systems.
Finally Accept the Difference