From what you are saying, I can conclude that you are using very high scoring for statistical classifier (or basing solely on statistics). This is not an option for a system with millions of users (their accept/reject rate is close to 70/30 percents, as we cannot rely on bayes at all). Therefore, I've never ever evaluated bayes as a single classifier. Nevertheless, I'm using OSB-Bayes as a statistical algorithm for rspamd which has been proven to be a good classifier.