Yesod vs. Trailblazer vs. webapp2

Yesod believes in the philosophy of making the compiler your ally, not your enemy. We use the type system to enforce as much as possible, from generating proper links, to avoiding XSS attacks, to dealing with character encoding issues. In general, if your code compiles, it works. And instead of declaring types everywhere you let the compiler figure them out for you with type inference.

Trailblazer is a thin layer on top of Rails. It gently enforces encapsulation, an intuitive code structure and gives you an object-oriented architecture. In a nutshell: Trailblazer makes you write logicless models that purely act as data objects, don't contain callbacks, nested attributes, validations or domain logic. It removes bulky controllers and strong_parameters by supplying additional layers to hold that code and completely replaces helpers.

webapp2 is a simple. it follows the simplicity of webapp, but improves it in some ways: it adds better URI routing and exception handling, a full featured response object and a more flexible dispatching mechanism.