Flask vs ASP.NET Core

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.

Thanks to breakthroughs in ROSLYN compiler and the efforts of the .NET COre developer team, code written in C# can reach speeds just a step behind C++.

Can run on Windows, Linux and Mac (also Visual Studio Code editor).

In .NET Core 2.1 and 3.0, new APIs are added that make it possible to write JSON APIs that require less memory, using Span<T> and UTF8 strings, and improve throughput of applications like Kestrel, ASP.NET Core web server. See also Utf8JsonReader.

Both microsoft and 3rd party tutorials are mostly of high quality and encourage you to use the industry best-practices.

Built-in middleware featuring: Authentication, Cookie policy, Health Check, MVC, Session etc.

Ability to host on IIS, Nginx, Apache, Docker, or self-host in your own process.

It is a very secure platform.

Both VS and VSCode are powerful free IDEs that are well integrated with ASP.net Core. VS Community also allows for commercial use for projects with less than 5 developers.