1. Architecture: Leaf PHP is a lightweight PHP framework that follows the MVC (Model-View-Controller) architecture, whereas Lumen is a micro-framework that is built on Laravel's components and architecture, focusing on speed and simplicity.
2. Performance: Lumen is faster than Leaf PHP due to its minimalistic design and emphasis on speed. It is designed for building small, fast microservices and APIs, while Leaf PHP is more suitable for general web applications.
3. Dependencies: Leaf PHP requires fewer dependencies to be installed compared to Lumen, making it easier to set up and maintain. Lumen, on the other hand, leverages the full power of Laravel's ecosystem, resulting in a larger footprint and more complex setup process.
4. Features: Lumen provides a subset of the features available in Laravel, offering a streamlined and focused set of functionalities for building fast and efficient applications. Leaf PHP, on the other hand, is more versatile and includes a wider range of features for web development.
5. Documentation: Lumen has comprehensive documentation that is well-maintained and supported by the Laravel community, making it easier for developers to learn and dive into the framework. Leaf PHP, while also having documentation available, may not be as extensive or regularly updated as Lumen's.
6. Community Support: Lumen benefits from the strong community support of Laravel, with a large number of developers actively contributing to its growth and development. Leaf PHP, being a newer and less widely adopted framework, may have a smaller community and fewer resources available for support and troubleshooting.

In Summary, Leaf PHP and Lumen differ in terms of architecture, performance, dependencies, features, documentation, and community support, catering to different needs and preferences in web development.