1. Key Difference 1: Build Configuration Language - Make uses a declarative build configuration language which specifies the dependencies and commands to build a target, whereas SCons uses a Python-based build configuration language that allows for more flexibility and programmability in defining the build process.

2. Key Difference 2: Dependency Tracking - Make uses timestamp-based dependency tracking to determine which files need to be rebuilt, while SCons uses a signature-based dependency tracking system that takes into account the content of the files to accurately determine if a target needs to be rebuilt.

3. Key Difference 3: Cross-platform Support - Make is a Unix-based build tool and may require additional configuration to work on other platforms, whereas SCons is designed to be cross-platform and can work seamlessly on different operating systems without much modification.

4. Key Difference 4: Parallel Building - Make builds targets sequentially by default, although it supports some limited parallelism. On the other hand, SCons has built-in support for parallel builds, making it more efficient for large-scale projects with numerous dependencies.

5. Key Difference 5: Customization and Extensibility - Make provides limited customization options through variables and macros, but it can be cumbersome to extend its functionality beyond the built-in features. SCons, being based on Python, allows for extensive customization and extensibility through scripts, making it more suited for complex build processes.

6. Key Difference 6: Performance and Scalability - Make can suffer from performance degradation and scalability issues with large projects, as the evaluation of the build graph becomes more time-consuming. In contrast, SCons has been designed with performance and scalability in mind, utilizing efficient algorithms and data structures to handle complex build graphs effectively.

In summary, Make and SCons differ in their build configuration language, dependency tracking mechanisms, cross-platform support, parallel building capabilities, customization options, and performance and scalability aspects.