I dont know the ins and outs enough myself to be able to comment properly, especially when there are less powerful versions of VR out there but if I remember right each screen has to be viewed at least at 90fps for comfort reasons which is one reason for needing all the power you can get.
Thats also why I'm continually impressed by how positive the reactions from people trying out PSVR seem to be.
I ended up cancelling my preorder for it for financial reasons but it still looks like a really nice piece of tech.