1. Server-side rendering (SSR) vs Client-side rendering (CSR): A key difference between Next.js and Rocket is their rendering approach. Next.js supports server-side rendering, which means that the server renders the components before sending them to the client's browser. This allows for faster initial loading times and improved SEO. On the other hand, Rocket uses client-side rendering, where the rendering happens on the client's browser using JavaScript after the initial HTML and CSS have been loaded. This can result in slower initial loading times but allows for more interactive and dynamic experiences.

2. Routing: Next.js provides automatic routing, meaning that you don't need to set up individual routes for each page. It automatically generates routes based on the file structure in the project. Rocket, on the other hand, requires explicit routing configuration using its routing macros. You need to define the routes explicitly, specifying the corresponding handlers.

3. Language/Framework: Next.js is built on top of React, a popular JavaScript library for building user interfaces. It provides a framework for server-side rendering React applications. Rocket, on the other hand, is written entirely in Rust, a systems programming language known for its performance and safety.

4. Build and Deployment: Next.js simplifies the build and deployment process by providing a ready-to-use build command. It also supports easy deployment to platforms like Vercel, making it convenient for deploying Next.js applications. In contrast, Rocket requires manual configuration and handling for building and deploying Rust applications. This might require more effort and expertise in Rust development and deployment workflows.

5. Package Ecosystem: Next.js benefits from a rich ecosystem of packages and libraries built for React. It can leverage these packages to enhance the development experience and add additional functionalities. Rocket, being a Rust framework, has access to a different set of libraries and tools in the Rust ecosystem. The choice of ecosystem depends on the specific needs and requirements of the project.

6. Maturity and Community: Next.js has been around for a longer time and has a more established community. It has been widely adopted by developers and has a larger pool of resources, tutorials, and community support available. Rocket, being relatively newer, has a smaller community and fewer resources. However, the Rust community is known for its quality and focus on performance, which can be advantageous for some projects.

In Summary, Next.js and Rocket differ in their rendering approach, routing mechanism, language/framework, build and deployment process, package ecosystem, and maturity/community support. The choice between them depends on the specific requirements, preferences, and expertise of the development team.