A newsletter subscriber list is incredibly higher in value than most blog visitor traffic. They have chosen to subscribe, you can contact them. You don't know

A newsletter subscriber list is incredibly higher in value than most blog visitor traffic. They have chosen to subscribe, you can contact them. You don't know your RSS subscriber count. It is a more highly engaged group, easier to build a relationship with. And the number of people using RSS compared to using email who would consider a newsletter subscription is tiny.