From my perspective, it's better as a data structure because I can do more with it. It's much easier for me to introspect, and I can easily build dynamic state

From my perspective, it's better as a data structure because I can do more with it. It's much easier for me to introspect, and I can easily build dynamic state-machines by changing a data structure, take a look at interceptors[0] as an example. There the stack is dynamically alterable based on what is within the request and each piece of middleware can look at the current context, analyse it and behave accordingly. I write a lot of workflow based systems with dynamically changing functionality based on user input. This sort of thing is invaluable in that context. - [0]: http://pedestal.io/guides/what-is-an-interceptor http://pedestal.io/guides/what-is-an-interceptor