Far simpler if you can include the fact that with Kubernetes you can install new applications as simply as "helm install prometheus".
I wasn't aware they were offering fargate on EKS now. They weren't when I looked at it last.
My big issue with it is the underlying complexity and house of cards nature of running your control plane as sidecar containers on your runtime infrastructure.
You CAN set it up and run the control plane out of band, but last I looked there wasn't step by step documentation for doing so. I also couldn't find anyone doing it in prod which to me is a nonstarter. If I can't figure it out myself and can't hire for it I'm not doing it.
I'm sure it's fine on google cloud, but ECS solves 90% of our problems AND integrates with everything else we're using already.
We went with ECS and have been happy with it. It plays well with all of AWS's other products and features. For the few things we have to run On-Prem we use Docker Swarm in single node mode and it works well (albeit missing a few features like crons from Kubernetes).