Li3 vs Leaf

Lithium has unified the relational and non-relational database APIs into a single one. Being one of the few frameworks to do it.

Lithium makes use of PHP namespaces to create a powerful plugin architecture. Almost every component of the framework is replaceable.

This framework loads faster than most due to its class autoloader. It is flexible as well and handles older classes - but requires the developer to define transforms here for naming convention, includes, etc. Many other frameworks use Composer for autoloading and that significantly slows down their bootstrap time because Composer's autoloader is extremely compatible without much developer interaction (it does not require as much involvement for autoloading legacy libraries). So it's a trade-off, speed vs. a little bit of up-front work.

Lithium comes with integrated unit testing. It also has a test dashboard.

Lithium's filter system is based on the paradigm of Aspect-oriented programming which aims to increase modularity by separating cross-cutting concerns and helping speed up development.

Lithium can return JSON and many other formats from the same actions that render templates increasing productivity in many cases. It handles a "type" key in the route which allows it to render various responses with different Content-Types. This is incredibly useful and easy to extend. This combined with closures in routes makes Lithium a very good framework for building a RESTful API.

Leaf has a simple structure and easy code.

Contains classes for managing requests, responses, cookies, logging, views, HTTP caching, and more.