If evaluated both for a client, and while they are separate products, they are almost identical in feature set. I wouldn't even say that you get "a lot" more c

If evaluated both for a client, and while they are separate products, they are almost identical in feature set. I wouldn't even say that you get "a lot" more control with the Assistant API, as in the end the flow of conversation will still be mainly driven by OpenAI. The main reasons why one would use the Assistant API is deeper integration and control about context initialization. On top of that, as you are responsible for rendering, you can create more seamless experiences and e.g. provide custom visualizations or utilize structured output an a programmatic way. Major downside of the assistant API is that you are also forced to build the UI yourself as well of the backend handling of driving the conversation flow forward via a polling based mechanism. If you want to build something quick without a lot of effort custom GPT + actions via an OpenAPI spec are the way to go in my opinion.