[steejk]

It depends what you want to do. If you want to access many chat apps a framework will make your life easier and provide some features such as analytics but at the expense of latency and inability to access any features specific to a particular chat application.

Wit.ai, API.ai etc. are separate services to which you forward your chat responses and they send back a response based NLP training etc.

If you're just doing a prototype, I would limit it to one chat app (eg. FB messenger) and interact directly with their webhook. You can also then add NLP through api.ai etc.