Who's the better fullback - Billy Slater or Jarryd Hayne?

Slater is the best fullback in the game. Hayne is playing fullback to fill a gap in the the Eels roster. Hayne is a utility player that can fill in at a number of positions, so, if the question was who is the better player, perhaps the answer would be Hayne but as specialist fullback he is not a patch on Slater.