Questions like this may easily start a fight on the forum. 
In principle it doesn’t matter because UE4 does a pretty good job at abstracting from any specific implementation and letting your work with standardized objects/functions, regardless of whether you are developing with an Oculus Rift, an HTC Vive or something else.
In practice, as you learn more and more, a time will come when you will want to go beyond some of the limitations any abstraction bring along and maybe add your own features. Then it becomes a matter of what you prefer and like most, or what you became familiar with in the meantime.
I would say go to a shop (or to friends) where you can experience both systems and pick the one you like most. I personally develop on the Oculus Rift because this is what I started with, but also because of their roadmap and vision for the future. So far it has served me well, but I know many others who are equally happy with their HTC Vive.