Constant Contact and ConvertKit are both email marketing service providers, but they have different features and approaches. Constant Contact is designed for mass email campaigns with tools to create newsletters, surveys, and discounts. It also offers a wide range of targeting options, including list segmentation, detailed tracking and analytics, a built-in CRM, and integration with Google and Salesforce. ConvertKit is more focused on building relationships and helping independent content creators and bloggers earn money through their lists. It has simplified automation functionality and has powerful but easy-to-use visual automation builders, flows for managing subscribers, and affiliate marketing features. ConvertKit offers fewer features than Constant Contact but is more intuitive and beginner-friendly.