Originally posted by Arhael
"On Attack of the Clones, I had to give them levels," he (Nick Gillard) said, "Sidious is a level nine . On this film, Obi is eight - he's moved up - Anakin is a nine; Mace is a nine, Yoda is a nine. They're up there with Sidious"Page 133, The Making of ROTS.
Here it explains that Anakin becomes level 9 by turning to darkside:
http://www.cinemareview.com/production.asp?prodid=2965Anakin is better than Kenobi, silly to argue otherwise.
Nick Gillard also said, Obi-Wan and Anakin 'just matched each other perfectly' so he is inconsistent about Anakin's power, and if he was 9 while Obi-Wan 8 there is no way that Ob-Wan could beat Anakin in mustafar. It should be stalemate at best.
And these sources also says they were equals as well ;
Still, the fight continued, even as the collection tower sank slowly into the lava. And still, neither man could gain an advantage.
- Source: Revenge of the Sith Junior Novelization
Years of fighting side-by-side left these warriors evenly matched, and their exhausting duel crossed the fiery landscape of a Mustafar refinery.
- Source: Lightsabers: A Guide to the Weapons of the Force