Both are container orchestration services. ECS is very well integrated with other Amazon Web Services. Kubernetes is cloud-neutral. You can find a good overview here

Your requirements should tell you which one makes more sense for your needs. Here are some tips to help you understand how each product is positioned. Of course, there's a lot of overlapping and both products are very able to run a production workload.

Go Kubernetes (or EKS, the AWS Managed Kubernetes service) if:

• You want cloud portability;
• You want to deploy on-premise;
• You want your developers to use the same tools that run your production workload.

Go ECS (or Fargate, its managed version) if:

• You are comfortable configuring AWS (eg: auto-scaling groups, VPCs, elastic load balancers...);

• You already have a workload running on EC2 and is gradually migrating it to containers;

• You look for a service that is easier to learn;