Ask HN: Kubernetes or ECS

For a team with about 40 million site visitors annually, would you suggest Kubernetes or ECS? (personally I am still trying to make the argument for monoliths but everyone seems hellbent on containers)

More context: We use AWS for everything. The arguments are AWS already manages it for us, and for what we want to do with it, it will be just fine. My argument is everyone seems to be favoring Kubernetes and saying ECS will always be playing catchup to k8s but I am still trying to learn why as I am getting reacclimatized with container orchestration. The last time I dabbled with this, I ran my own core-os cluster and used etcd with haproxy and registrator, but it seems like there are new tools now and I am trying to get back into the game.

So in short, for a small team with medium traffic that wants to go containers, and most of their infrastructure on AWS (plus we like to use other amazon offerings), ecs or k8s? Pros and cons? Thank you so much.