How would you compare the available game engines for developing VR?
Which engines have you tried with VR projects?
What pros and cons have you experienced?
What do you think would improve Unity the most, to make it the go to VR game engine?
Both Unreal and Unity work well for VR(Desktop). Both have plug and play and in editor support.
Unreal for a Viz project and Unity for simulations and testing theories.
Neither have any major pro/cons to me. Unreal is more resource intensive, but has a good scaling option with the sp command.
Unity is the go to VR for most right now.
I would be inclined to choose Unreal. They appear to be putting quite a bit of effort into virtual reality support. The latest update includes support for motion controllers through a common interface.