I've used online VR viewers in the past and was mostly dissapointed in their quality. I mean they're great for a quick review of a CAD model and require little to no effort to set-up, but this also means little to no added value.
Lately I - , and other persons in my design team, are using Unity3D (https://unity3d.com/
) to review and render 3D models in VR and create real-time renders and small animations. So far it's working great.
Unity is relatively easy to learn if you know the coding basics. And even without these, the main site has loads of tutorials to get started on basic VR development.
If you model in CAD-software that has the option to extract the UV-mappings of the model, making realistic models is relatively straightforward. It's not exactly Keyshot click and drag but basic photoshop skills do the trick.
The great benefit of Unity (and other game-engines such as Unreal) is the big community behind it, with loads of active VR developers.