MWAA vs Step Functions

There is already answer in another forum: https://stackoverflow.com/questions/64016869/airflow-versus-aws-step-functions-for-workflow. More info on the choice can also be found in https://aws.amazon.com/managed-workflows-for-apache-airflow/faqs/

Step Function is serverless version of workflow management.

Airflow / MWAA is open-source and server-based. Some people are more familiar with Airflow and would like to reuse their Airflow experience in AWS but prefer to not manage servers so much. In that case, they should pick MWAA.