Hey @Constantin Teo!
Marvin was our first foray into AI DX, but the vast majority of its features are not about agentic behaviors or iterated AI actions. If you use Marvin to extract information, the classify it, you're making two independent calls to an LLM. That may be completely fine for your use case.
ControlFlow is designed for workflows that require iterated invocations or AIs that use tools to create side effects and need to react. A lot of Marvin functionality is straightforward in CF (in fact, every individual CF task is essentially a Marvin function), but CF is adding a layer of automatic state tracking that Marvin lacks.