1. Architecture: Locust is a distributed and scalable tool that allows the simulation of thousands of concurrent users, making it suitable for load testing. On the other hand, Postman is a single-user tool designed for manual and automated API testing, focusing more on the functional testing aspect.

2. Testing Approach: Locust follows a behavior-driven testing approach, where test scenarios are defined using Python code. It allows the creation of complex test scenarios with custom user behavior. In contrast, Postman uses a request-driven approach, where tests are created by sending HTTP requests and validating the responses. It provides a user-friendly interface for designing and running tests.

3. Scripting Capabilities: Locust provides complete flexibility in scripting and customizing user behavior. It allows the use of Python code to define tasks, user actions, and request parameters. Postman, on the other hand, also supports scripting but uses JavaScript instead of Python. The scripting capabilities in Postman are more limited compared to Locust.

4. Load Generation: Locust is designed specifically for load testing and distributed load generation. It can spawn thousands of virtual users on multiple machines, simulating realistic load scenarios. Postman, though capable of handling multiple requests simultaneously, is not specifically optimized for high-scale load testing. It is more suitable for functional testing and integration testing.

5. Reporting and Analysis: Locust provides real-time monitoring and reporting of performance metrics such as response times, failure rates, and throughput. It also offers integration with various monitoring and analysis tools. Postman, on the other hand, provides limited reporting and analysis features. It offers basic reporting on test results but lacks advanced performance monitoring capabilities.

6. Collaboration and Team Features: Postman provides extensive features for collaboration and team-based API testing. It allows team members to share and collaborate on collections, APIs, and test scripts. It also provides features like version control, team libraries, and API documentation. Locust, being primarily focused on load testing, lacks the built-in collaboration and team features offered by Postman.

In Summary, Locust is a scalable tool for load testing with powerful scripting capabilities, while Postman is a user-friendly tool for functional testing with collaboration features.