1. Markdown Support: Pandoc has excellent support for Markdown, allowing users to write content in a simple and readable format and then convert it to various output formats such as HTML or PDF. Sphinx, on the other hand, primarily relies on reStructuredText for documenting technical projects, which has a steeper learning curve and might not be as straightforward for those familiar with Markdown.

2. Documentation Focus: While both Pandoc and Sphinx can be used for documentation purposes, Sphinx is specifically designed for creating technical and API documentation, making it a preferred choice for developers and programmers. Pandoc, on the other hand, is more versatile and can be utilized for various documentation types, including academic papers, books, and web content.

3. Extensibility: Sphinx offers a powerful extension mechanism that allows users to customize and extend its core functionality. This feature is especially useful when creating complex technical documentation, as it allows for the integration of additional tools and functionalities seamlessly. In contrast, Pandoc provides a limited extension mechanism and may require more manual customization to achieve the desired output.

4. Built-in Static Site Generator: Sphinx comes with a built-in static site generator, enabling users to easily create and maintain a static website from their documentation. This is particularly advantageous for projects requiring continuous updates and live documentation. Pandoc, however, does not provide a built-in site generator and might require additional tools or workflows to achieve a similar result.

5. Output Formats: Pandoc supports an extensive range of output formats, including HTML, PDF, EPUB, and DOCX, making it highly versatile in terms of delivering content in various formats. Sphinx, on the other hand, primarily focuses on generating HTML and PDF output, which may limit its capabilities for projects requiring other formats, such as ebooks or Word documents.

6. Community and Ecosystem: Both Pandoc and Sphinx have active communities and ecosystems around them, providing users with resources, plugins, and support. However, Sphinx's community is more oriented towards the technical and developer community, providing a wide range of extensions, themes, and integrations specifically tailored for technical documentation. Pandoc's community, on the other hand, caters to a broader range of use cases, including academia, publishing, and general document conversion.

In summary, Pandoc and Sphinx differ in terms of their focus (versatility vs. technical documentation), support for Markdown, extension mechanisms, built-in site generation, output formats, and community ecosystems. Choosing between them primarily depends on the specific needs and requirements of the documentation project at hand.