Definitely Maia. Faber was a pioneer and a fun fighter to watch but he was never part of the elite. Maia was a top 5 level fighter for about a decade and only had problems due to match-ups which is just inevitable for particular styles, but he never got handled or destroyed by someone. Faber on the other hand looked pretty bad when he had to go up against guys like Aldo, Cruz or Barao. You just saw that the best of the best were a couple of steps ahead in every aspect of the game. His time was back when the lower weight classes still didn't have much spotlight and were in the developing phase, he was one of the guys that managed to rise to the top there rather quickly. Of course the competition of that time can't be compared to what you've had in Bantamweight and Featherweight this decade.