Please forgive me if I missed this in some of the comments and replies, but I saw nothing on Infusionsoft or Marketo. I was expecting to see both in your analysis, but nothing was mentioned, save for the remark early on that Active Campaign has rocketed past Infusionsoft in the marketplace. Is it because you consider them outside the “Email Marketing” space which was the subject of your analysis?
Here's another great example from Litmus of animation being used to create more interesting email marketing design. Unlike static text, the swipe motion used to provide recipients with a look "under the hood" of their email tool is eye-catching and encourages you to take a deeper dive into the rest of the content. Not to mention the header does an excellent job of explicitly stating what this email is about.
Sample review: Optinmonster “has various forms you can embed on your site to help with email conversion but one of the most interesting ones is the popup. You can set the popup only to appear on ‘exit intent’. This means that your website visitor can browse all they want and when they are about to exit the website you can have a popup appearing tempting the visitor to leave their email address.” — RazorSocial (World)
A tracking pixel is a snippet of code that allows you to track your subscribers’ activity across various channels like your website, landing pages, and newsletters. Then, you also have the option to send emails triggered by certain behaviors. So for example, if a subscriber goes to your site and checks out your product page, a tracking pixel can send an email with a special offer for the specific product the viewed.