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.
These often compact agencies or single experts are specialized in email deliverability. Making sure that the email hits the inbox. They are able to solve deliverability (email goes to spam!) problems. Think about managing on-premise or their own servers, or otherwise once there is some real concern / problems with email deliverability, blacklisting, etc.
Companies considering the use of an email marketing program must make sure that their program does not violate spam laws such as the United States' Controlling the Assault of Non-Solicited Pornography and Marketing Act (CAN-SPAM), the European Privacy and Electronic Communications Regulations 2003, or their Internet service provider's acceptable use policy.
And that leads us right into understanding service pricing and packaging. The email marketing services we reviewed range from about $5 per month to as much as $20 per month for a range of features. Many email marketing plans include unlimited email sends each month and bill you based on the number of subscribers. If you have a small list, then look for a company that offers a free plan, a low-cost plan for several hundred subscribers, or even a pay-as-you-go plan. On the flip side, many of these services also offer high-volume plans with up to 100,000 or more contacts. Sometimes this requires a custom plan that has to be arranged directly with a sales rep. If you're willing to commit, then look for the companies that offer discounts if you pay yearly rather than monthly. A few offer also money-back guarantees.
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.