Scotty vs wai-routes
When comparing Scotty vs wai-routes, the Slant community recommends Scotty for most people. In the question“What are the best Haskell web frameworks for building RESTful web services?” Scotty is ranked 5th while wai-routes is ranked 6th. The most important reason people chose Scotty is:
A simple framework cuts development time and costs. To get started, developers only need to understand how to write routing and actions.
Ranked in these QuestionsQuestion Ranking
Pros

Pro Easy to pick up and use
A simple framework cuts development time and costs. To get started, developers only need to understand how to write routing and actions.

Pro Available on gitHub
Having the source code on gitHub means developers can easily suggest improvements and error reports. They also have a community that can help with any problems that come up.

Pro Provides type-safe routes
Automatically maps routes to datatypes which are checked at compile time. It uses Template Haskell to reduce boilerplate.

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

Pro Easy to customise
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.

Pro Lightweight
Performs quite well when compared with other Haskell web frameworks.

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

Pro Provides nested routes
Nested routes allow reduction of boilerplate code.

Pro Route annotations
Route annotations provide an easy way to "mark" routes for extra processing.
Cons
Con Lacks features due to its small size
Since Scotty is small, it does not contain some features that a complex web application may need. Anything that Scotty can't provide must be either found or written, costing developers.

Con Learning curve
Even though it's a "micro" framework, it has a steep learning curve when using advanced features such as subsites.
Alternative Products
