Hazard's the better player, this all started though with Ronaldo saying he had lees than half of Hazard ability which isn't true. In terms of ability he really isn't far off. He's just less consistent, mentally stable as well as works less on the pitch at Hazard, all which makes Hazard such a good player.
But we have all seen what Ben Arfa is capable of doing on the pitch, some of the stuff he has done I doubt Hazard would be able to do tbh.