The problem I have is I want to choose a Private PaaS to install it on my own infra and provide a platform as a service to my own clients. I need something like OpenShift or Jelastic...
The most important factors for me are that it has to be on-premise support, extensible (we can add feature to it), supports containers (docker, lxc, ...) supports databases (MySQL, Redis, mongo...), support load balancers, support software-defined storages (ceph, minio,...) monitoring and we can sell it to our own clients.
Do you have any idea?
In your position I'd start by talking to customers and understanding their requirements. Unfortunately, although Apache Mesos + Marathon is generally liked more and simpler, it's still a commercially owned space when you run into trouble. On the other hand Kubernetes is more open and popular (check search results, about 10X) and customers like that they can move around among GKE and AWS and other Kubernetes environments. So although I think Kubernetes is overly complex for the newcomer, (and you may need Helm as well) it's going to be more popular with your customers. Also, Kubernetes is fairly open in terms of extensibility (esp if you work in Go lang).
More thorough discussions here:
* https://logz.io/blog/kubernetes-vs-mesos/
* https://www.stratoscale.com/blog/kubernetes/kubernetes-vs-mesos-architects-perspective/
Mesos-Enthuasiast may criticise me for my statement, but Kubernetes has simply won the race. Most companies I work with have a Kubernetes strategy. With that backing the platform will continue to grow whereas Mesos will become a niche.