You can use any of these services to add Natural Language Understanding (NLU) capabilities to your Botonic bot. Think of it as a piece inside a larger architecture. You can, of course, build your bot entirely with Dialogflow, for instance, but there are many scenarios where this is not the right choice.
First, modern conversational experiences mix decision trees, NLP, webviews and human handoff. The AI-centric approach of tools like Dialogflow might not be the best for your use case. Actually, 80% of successful chatbots in WeChat are guided experiences (decision trees with no AI at all).
Second, if you're a developer, you'll feel more comfortable using a framework like Botonic that lets you build and test your bot locally, have it version controlled and deployable with a command-line interface. This means that Botonic integrates better into the developer workflow (Continuous Integration, Continuous Deployment, etc), on the other hand, Dialogflow and such force you to create/edit your bot in the cloud, which might be more suitable for non-technical people.
And last but not least, Botonic is open-source!