Big difference between Wordpress stats and server logs

Hi, I volunteer as co-editor and main tech person for an academic collaborative blog. In our most recent full calendar month (October 2017), there was a 4-fold difference between the unique visitors reported by our server logs (Awstats) and what was reported by Wordpress.com. Why? We host our blog on our own domain and those are the only two stats programs I have access to. The big difference last month is not unique - in most months, Awstats/server logs are showing 4 times more unique visitors to our blog. Whom do we trust - the webhost or Wordpress? And why the big discrepancy? I have searched the web and the AskMe archives as well as both Wordpress and server help files, with no success.

Feel free to also recommend any good resources for non-profit web management and analytics. Thanks in advance for your help!