MailChimp have recently improved there interface greatly, feels more robust and is free for up to 2000 subscribers.

Mailpoet integrates with your WordPress website admin interface and media library so you’ll be in a more familiar environment. Mailpoet is free for up to 1000 emails. – 3rd party email service – integrated with your self-hosted WordPress website

Mailpoet Pros

  1. Mailpoet uses the WP Media library and has benefit of familiarity with the WP admin interface
  2. Free for up to 1000 emails
  3. No extra login/security requirements
  4. Latest posts automatically added to newsletters

Mailpoet Cons

  1. Maintenance (upgrades etc) are your responsibility – but are covered by Loud Mountain Support Service
  2. Less functionality options than Mailchimp (but this can be a benefit depending on your needs)

Mailchimp Pros

  1. Hosted 3rd party solution – no upgrades required
  2. Free for most people’s needs
  3. Seems more robust and backed by a huge company

Mailchimp Cons

  1. New interface to learn
  2. More complex due to more features

Review by priority

  • Ease of use (both the content creation and the mailing list management).
    Posts can automatically be added to Mailpoet. Both use a form to add new subscribers and have multiple mailing lists.
  • Appearance of output (on various devices).
    Same for both.
  • Sharing content is simply a matter of copy/paste or duplicating a template, then customising. Therefore, same for both.