The problem I always here with Mesos is that it doesn't scale down well. I.E., that it is not developer friendly or, to put it another way, you can't run it on your laptop.
However, your point is somewhat valid in that Mesos requires you to allocate resources to everything you run, while resource allocation/enforcement is optional in Kubernetes. So you can easily run too many things and freeze your computer with Kubernetes, while Mesos is more conservative.
