1. User Interface: Hoppscotch provides a clean and user-friendly interface that allows users to easily navigate through the testing process, while RapidAPI Testing offers a more comprehensive interface with additional features for API testing.

2. Authentication Methods: Hoppscotch supports various authentication methods such as OAuth, API keys, and Basic Auth, whereas RapidAPI Testing includes a wider range of authentication options like JWT, OAuth 2.0, and API key validation.

3. Environment Variables: Hoppscotch allows users to manage environment variables and use them in requests for efficient testing, while RapidAPI Testing also offers environment variables but with additional support for dynamic variables and preset values.

4. Mocking APIs: RapidAPI Testing provides a feature for mocking APIs to simulate responses, which is not available in Hoppscotch, giving RapidAPI an edge in creating a controlled testing environment without relying on actual API endpoints.

5. Monitoring and Analytics: RapidAPI Testing comes equipped with built-in monitoring and analytics tools to track and analyze API performance, while Hoppscotch lacks this feature, making RapidAPI a more comprehensive solution for testing and monitoring API performance.

6. Collaboration and Team Management: RapidAPI Testing offers collaborative features such as team management and role-based access control, allowing teams to work together efficiently on API testing projects, a functionality that is not available in Hoppscotch.

In Summary, the key differences between Hoppscotch and RapidAPI Testing lie in their user interfaces, authentication methods, environment variables management, API mocking capabilities, monitoring and analytics tools, as well as collaboration and team management features.