The main difference between Sender and Mailchimp is in the types of features they offer. Sender focuses heavily on email marketing automation while Mailchimp provides a more comprehensive marketing suite encompassing email marketing as well as automation tools, analytics, and additional integrations. Sender has more intuitive and precise automation capabilities, allowing more granular segmentation and automation of particular actions. Additionally, Sender offers more support for translating campaigns into different languages, making it ideal for those targeting multiple markets. Mailchimp, on the other hand, has more intuitive and comprehensive analytics, as well as a significantly larger library of pre-made templates. Both offer a good way to send campaigns, but each has their own distinct features that make them appropriate for different types of marketers.