I'd hardly call Istio something you "need". Between Docker and Kubernetes you'll have your hands well full enough already and I'd recommend getting a good grip on those first and avoiding the service mess until you are very convinced your life will be worse if you don't slap Envoy, Mixer, Pilot, Citadel, and Galley on top.
I think that the OP is looking for a standard/container based enterprise platform, so I would install both since only both provide the complete solution.
I.e. install and standardize on both, but start using features as needed (of course).
I.e. I would rather find out any architecture issues with istio sooner, than trying to bolt it on top of some kuberentes only app.
More complex != better.