I've run vanilla k8s for about 3 years now in prod but am also fairly familiar (and really like) Openshift Origin. I usually tell people asking this question the following;
OO comes with a bunch of really nice quality of life improvements that are missing (but in a lot of cases can be added via 3rd party TPR/CRDs/etc) in k8s but you aren't deviating so far from k8s that you won't be able to go work on vanilla k8s in the future. Not at all. Most of the additional stuff are annotations that simply wouldn't do anything and you'd remove them if you moved from OO to k8s.
I think that if you're brand new to the environment OO can really help you get running quickly. You just have to make sure that you do in fact dive in to the actual k8s yaml and deal with ingresses, prometheus, grafana, RBAC, etc at some point. I haven't used OO in awhile but I believe you could successfully do most of what I do day to day via yaml/json through the OO UI.
On the flip side a lot of people will probably tell you to start from k8s, whether that's GKE or AWS or minikube or wherever and go through the k8s the hard way. Personally, and I help people quite frequently on the k8s slack, I feel like that leads a lot of people down a path of frustration. It may be perfect for your style of learning or it may just scare you off.
Now when it comes to OO you are at the behest of their releases. Their most recent release was Nov 2017 and k8s 1.10 was just cut. I'm not sure what version OO is on now, evidently they changed their versioning numbers to not correspond to the k8s version.
Join #kubernetes-users and #kubernetes-novice on slack.k8s.io if you need any help. It's a vibrant community. You can message me directly @ mikej if you'd like.
edit: Ok OO 3.7 is k8s 1.9, that's perfect. I wait a few months before jumping into new major.
I'm not a production user, but I've had a look at both. From what I've seen OpenShift provides a more polished and complete package than base Kubernetes, so if you're looking to get productive quick, it's probably a good option.
Kubernetes base is more flexible of course, but with that flexibility comes more stuff you have to do yourself...
Either way they're both based on the same tech., so experience with one largely translates across to the other
Kubernetes is great for those that are ops-inclined, OpenShift is a much better experience for your typical developer though.
Personal anecdote: We've had OpenShift Origin running in production for a year and a half, I'm the DevOps guy and know how to poke around in the internals but the developers on my team are just that, developers. They just want to say "here's my code, go make it work", S2I, templates and Jenkins pipelines let them do just that - they go paste the URL of a git repository into the web interface and watch the project build and automatically deploy. It's a pretty magic experience watching a Junior developer deploy 13 applications over the course of a year with no supervision or hand-holding from a more-senior developer.
I deployed plain k8 to start with 2 month back and started adding more add-ons and plugins as we go. This made us be flexible abt what we use and control. So far no issues.
Also our customers are inclined for k8 workload files not OpenShift.
