Yesod vs wai-routes

While not required, Yesod offers templating through a Shakespearean family of languages to produce page code.

Ensures that data provided by the URL is type-safe. This means that data in the URL has a definitive type.

While Yesod is written in Haskell, developers can achieve basic functionality without much investment in the language.

Automatically maps routes to datatypes which are checked at compile time. It uses Template Haskell to reduce boilerplate.

Can be used without any routing or Template Haskell. "Unrouted" handlers can be freely mixed and matched with typed routing and middleware.

Wai-routes is extremely easy to customise. It's neutral to other parts of the system such as the templating language, or the wai server being used. Wai-routes only targets and provides full access to the wai API. The wai-routes handlers are also simple functions which are passed the request data and the environment and return a Response in IO. Arbitrary middleware, routes, and handlers can be mixed together to construct an application.

Performs quite well when compared with other Haskell web frameworks.

Subsites provide encapsulation and ability compile time enforcement of contracts between main site and subsites.

Nested routes allow reduction of boilerplate code.

Route annotations provide an easy way to "mark" routes for extra processing.