1. Key difference 1: GWT is a framework for building web applications using Java and a set of libraries that compile Java code into JavaScript, while Spring is a framework for building enterprise Java applications that provides a comprehensive infrastructure support GWT focuses on the client-side development of web applications, enabling developers to write Java code that can be compiled into JavaScript and run on the client-side. On the other hand, Spring provides a robust infrastructure for building enterprise Java applications, including features like dependency injection, transaction management, and aspect-oriented programming.

2. Key difference 2: GWT emphasizes on the development of rich user interfaces through its UI functionality, while Spring focuses on providing a flexible and modular architecture for building enterprise applications GWT provides a rich set of UI components and widgets that can be used to build visually appealing and interactive user interfaces. It also includes features like data binding, event handling, and layout management. In contrast, Spring focuses more on providing a flexible and modular architecture for building enterprise applications, with features like inversion of control and aspect-oriented programming.

3. Key difference 3: GWT uses a client-server architecture with an emphasis on client-side rendering, while Spring uses a server-centric architecture with server-side rendering GWT follows a client-server architecture, where the client-side code is written in Java and compiled into JavaScript, which is then executed on the client-side. The server-side code usually provides data and business logic to the client code. On the other hand, Spring follows a more traditional server-centric architecture, where the server-side code is responsible for rendering the user interface and executing business logic.

4. Key difference 4: GWT provides a development mode for fast iterative development and debugging, while Spring focuses on providing a robust and scalable runtime environment GWT includes a development mode that allows developers to run and test their applications directly from the development environment, without the need to compile the code into JavaScript. This greatly speeds up the development and debugging process. Spring, on the other hand, focuses more on providing a robust and scalable runtime environment for enterprise applications, with features like load balancing, clustering, and caching.

5. Key difference 5: GWT has built-in support for mobile development, while Spring is more focused on server-side development GWT includes built-in support for mobile development, allowing developers to build mobile-friendly web applications. It provides features like responsive design, touch events, and device detection. Spring, on the other hand, is more focused on server-side development and does not have specific features for mobile development.

6. Key difference 6: GWT has a strong integration with Google services and APIs, while Spring provides integration with a wide range of third-party libraries and frameworks GWT has a strong integration with various Google services and APIs, allowing developers to easily use services like Google Maps, Google Charts, and Google Analytics in their applications. Spring, on the other hand, provides integration with a wide range of third-party libraries and frameworks, allowing developers to leverage the capabilities of these libraries in their Spring applications.

In Summary, GWT focuses on client-side development using Java and provides rich UI functionality, while Spring is focused on server-side development of enterprise applications with a flexible and modular architecture.