Ask HN: Unreal Engine or Unity for Long-Term VR Project?

I'm a software developer and this is my first experience with 3D and VR. I planned to create a small prototype for Social VR project and I want to find the best fit for that.

They both seem equally good at first glance and the underlying languages (C++/Blueprint and C#) are not the problem.

Does anybody know pros and cons of these engines when it comes to VR?