The interface of DCOS really is excellent, the default project for kubernetes doesn't even come close, especially the 1.9 release of DCOS polished everything up. It does have its quirks though. Which does force you to use the json editor sometimes.
But the openshift UI is also very nice, I've been using it through the CDK with minishift and it's an excellent interface for kubernetes/openshift.
Even the OpenShift UI forces you to drop into a yaml editor every now and then. Kubernetes is too powerful to really represent in any UI without a ton of work - which is really the central decision when adopting Kube. Do you want the power available if you need it? Or do you want something simpler that might constrain a future choice?
Of note, there's a structured web editor for any API resource in Kube, OpenShift, or extension being prototyped now that I'm hoping helps bridge that gap.
Also, check out the latest nightlies or 3.6.0-alpha.2 for a bunch of massive improvements to the overview - I think it's easily the biggest enhancement over the last few years.
There are some nice features of the UI in OpenShift that I'm missing in the kube dashboard, such as the terminal.
Also the ability to split up access to workspaces in OpenShift could be useful, though I don't know if that's accomplished with actual API objects or whether it would map onto kube.
I believe DCOS has a really nice interface.