Flask vs Lumen

Flask is very easy to get up and going, with vanilla HTML or with bootstrap pieces. It doesn't take much lines of Python to load Flask to get headers working, etc, and since it's all modular you don't have to have something you don't want in your application.

Flask is one of the most popular Python web frameworks, if not the most popular one. As such, there's plenty of guides, tutorials, and libraries available for it. A large number of important Python libraries, such as SQLAlchemy have libraries for Flask, which add valuable bindings to make the development process and the integration between these libraries and Flask as easy as possible.

Even though it's pretty minimalistic out of the box, Flask still provides the necessary tools to build a quick prototype for a web app right after a fresh install. With all the main components pretty much packed in the flask package, building a simple web app in a single Python file is as easy as it gets.

Flask gives developers a lot of flexibility in how they develop their web applications.

For example, the choice of not having an ORM, but instead choosing one suited to the task, or another area where Flask gives a lot of options to developers is the templating. They can use Jinja2, Flask's default templating language or choose from a number of different templating languages they desire.

The official documentation is very thorough and complete. Everything is explained in-depth and followed by extremely well-explained tutorials that tackle real-world problems.

Since it's basically just a minimal version of Laravel, it can be upgraded to a full Laravel app if the need arises. No need for code changes, just import the code to a new Laravel install.

Lumen is benchmarked at 100/rps (Requests Per Second) faster than Slim v3, which used to be considered the fastest and most performant micro-Framework to date with the ability to handle 1800/rps. (1900/rps vs 1800/rps respectively).