GNU M4 VS PP - A generic Preprocessor - compare differences & reviews?

GNU M4 is an implementation of the m4 macro preprocessor.

P is a text preprocessor designed for Pandoc (and more generally Markdown and reStructuredText).

Portability
GNU M4 is highly portable and can run on almost any Unix-like operating system, which makes it versatile for various environments.
Macro Capabilities
It offers powerful macro processing features that are useful for a wide range of text processing tasks, such as configuring scripts, code generation, and templating.
Simplicity
M4 is relatively simple to use for basic macro processing tasks, which makes it accessible to new users and suitable for straightforward applications.
Integration
GNU M4 often integrates well with other tools and scripts, making it a useful component in build systems and automated workflows.

Limited Built-in Functions
Compared to more modern scripting languages, M4 lacks a wide range of built-in functions and features, which may limit its use for more complex tasks.
Steep Learning Curve
While simple tasks are easy to set up, mastering M4 for more advanced uses can require a deeper understanding of its syntax and capabilities.
Debugging Difficulty
Debugging macros in M4 can be challenging, especially for large scripts, due to the lack of advanced debugging tools and support.
Performance Considerations
For very large and complex scripts, performance may become an issue, as M4 is not optimized for handling large-scale data manipulation compared to more modern alternatives.

Flexibility
PP allows for extensive customization and flexibility in preprocessing tasks, enabling users to tailor the tool to their specific preprocessing needs.
Wide Language Support
PP is designed to work with a variety of programming languages, making it suitable for diverse coding environments and projects.
Open Source
As an open-source tool, PP is free to use and can be modified according to user requirements, promoting community collaboration and continuous improvement.
Simplicity
The tool provides a simple syntax and usage pattern, making it accessible to users who need efficient preprocessing without a steep learning curve.

Limited Documentation
PP's documentation might not be as comprehensive as some users would prefer, potentially making it difficult for newcomers to take full advantage of its features.
User Support
Being a less mainstream tool, PP may not have as large a user community for support, which could make troubleshooting more challenging.
Performance
For very large projects, PP may not be as optimized as other preprocessors specifically designed for high performance, possibly affecting execution speed.