Use MinIO when you need a self-hosted object storage solution that is compatible with S3 APIs but requires more control over your data, such as in a private cloud or on-premises scenario. A specific scenario would be if your organization has strict data privacy regulations and needs to store sensitive data locally, avoiding third-party cloud services.
You would use Amazon S3 over MinIO when you need a highly reliable storage solution that integrates seamlessly with other AWS services, especially in a production environment with stringent uptime and performance requirements. For example, if you are running a large-scale e-commerce application hosted on AWS, using S3 for static asset storage (like product images, videos, etc.) would leverage its global scalability and fast content delivery networks.