1. Programming Language: Fabric is written in Python, while Salt is written in a combination of Python and ZeroMQ. This difference in programming languages can impact developers' ease of use, familiarity, and flexibility in customization.

2. Architecture: Fabric follows a masterless architecture, where commands are run in a linear sequence on remote nodes, making it simpler for small setups. In contrast, Salt follows a master-slave architecture, allowing for more complex configurations, such as managing thousands of machines from a central location.

3. Scalability: Salt is designed to scale efficiently due to its master-slave architecture, making it suitable for large-scale infrastructures with numerous nodes. Fabric, being masterless, may face scalability challenges when managing a large number of machines simultaneously, leading to potential performance issues.

4. Extensibility: Salt provides more extensive built-in functionality and modules compared to Fabric, offering a broader range of features for configuration management, remote execution, and orchestration tasks. This makes Salt a more comprehensive solution for managing diverse infrastructure setups.

5. Community Support: Fabric has a smaller community compared to Salt, resulting in potentially slower bug fixes, updates, and a smaller pool of resources and tutorials available. Salt, with its larger community base, offers more extensive support, documentation, and community-contributed modules.

6. Learning Curve: Fabric is known for its simplicity and ease of use, making it a preferred choice for straightforward deployment tasks. On the other hand, Salt's multi-faceted architecture and extensive feature set may result in a steeper learning curve for users, requiring more time and effort to become proficient in its usage.

In Summary, Fabric and Salt differ in their programming languages, architectures, scalability, extensibility, community support, and learning curve, impacting their suitability for various infrastructure management needs.