Prefect is preferred when you need to create complex workflows with dynamic and flexible task dependencies. It's particularly useful in scenarios where tasks can change based on variable inputs, such as in ETL pipelines that adapt based on incoming data. For example, if your data ingestion pipeline needs to adjust the number of data processing tasks based on the size of the incoming data batch, Prefect's dynamic task generation will allow you to configure this easily.
Luigi is a good choice when you have simpler workflows or batch processing tasks that require clear dependencies and do not need real-time orchestration features. For example, if you are developing a data pipeline that involves regularly scheduled ETL tasks where tasks are well-defined and dependent on each other, Luigi's simplicity and clear task management can make it easier to implement and maintain.