Having used both DC/OS (mesos & marathon) and kubernetes in production.

The one thing DC/OS had absolutely nailed was the web interface and bootstrap. The DC/OS interface is brilliant as it allows you to explore all the possibilities and actually have a overview of what is happening.

Also, it was a lot easier to reason about because everything is contained in a single marathon job. No need to split everything up in deployments / services / ingresses. A single JSON file is all you need for DC/OS. Less to think about.

The downside of all this is that DC/OS feels like a solution for a theoretical problem, while kubernetes is the solution to practical problems.