From my understanding the engine is ready however there are a few things that the oculus market demands which are currently not implemented (volume buttons, proper “back” button as well as other important features, I have not looked into it that much as my product is no where near ready for release yet). As for performance I personally have not used Unity but from my understanding they currently have better performance. Epic had stated however that mobile improvements are currently being worked on. After viewing Gunjack ( http://m.youtube.com/watch?v=JF2aruO5jAY ) I just can not see that intro running 60 fps with the current engine so that builds confidence that mobile improvements truly are on the way.
These of course are my own personal opinions and they could be incorrect.