1. 1. Server-side rendering vs Post-processing: Next.js is a framework that allows for server-side rendering of React applications, meaning that the HTML for a page is generated on the server and sent to the client. On the other hand, PostCSS is a tool that processes CSS files after they have been generated, allowing for transformations such as adding vendor prefixes, minification, and more.

2. 2. Directly integrated vs External tool: Next.js has built-in support for CSS modules and supports importing CSS files directly into React components, allowing for easy and seamless use of CSS within the application. PostCSS, on the other hand, is an external tool that needs to be configured and set up separately in order to be used with a project.

3. 3. Styles scoped to components vs Global styles: Next.js encourages the use of CSS modules, which allows styles to be scoped to individual components. This promotes a modular and component-based approach to styling, making it easier to manage and understand the styles within a project. PostCSS, on the other hand, does not inherently provide a solution for scoping styles to components, and styles are typically written globally.

4. 4. CSS-in-JS vs Traditional CSS: Next.js supports CSS-in-JS libraries like Styled Components or CSS Modules, allowing for a more JavaScript-centric approach to styling where styles are written as JavaScript code. This provides benefits such as better code organization, dynamic styles, and the ability to use JavaScript variables and functions within the styles. PostCSS, on the other hand, follows the traditional CSS syntax with separate CSS files.

5. 5. Automatic code splitting vs No code splitting: Next.js automatically splits the code based on the pages, allowing for better performance by only loading the code that is necessary for the current page. This improves the initial page load time and reduces the overall bundle size. PostCSS does not provide any built-in code splitting functionality.

6. 6. Serverless deployment vs Post-build deployment: Next.js allows for serverless deployment using platforms like Vercel, where the application is deployed as serverless functions. This provides benefits such as automatic scaling, easier deployment process, and usage-based pricing. PostCSS does not have any specific deployment features and the deployment process would depend on the overall project setup.

In Summary, Next.js is a framework for server-side rendered React applications with built-in support for CSS modules and CSS-in-JS, automatic code splitting, and serverless deployment. PostCSS, on the other hand, is a tool for post-processing CSS files with a traditional CSS approach and requires separate configuration and setup.