This article is informative, but it does not offer distinguishing features between the services covered (other than mailchimp is free). You seemed to go to great lengths to say good things about each – although I’m sure each services has positive aspects. I would have benefited much more from a rating of some sort of the various features of each service, or at least the pros & cons of each.
In addition to satisfying legal requirements, email service providers (ESPs) began to help customers establish and manage their own email marketing campaigns. The service providers supply email templates and general best practices, as well as methods for handling subscriptions and cancellations automatically. Some ESPs will provide insight and assistance with deliverability issues for major email providers. They also provide statistics pertaining to the number of messages received and opened, and whether the recipients clicked on any links within the messages.