Mustafar Vader>BoROTS Anakin confirmed

Anakin's emotional shifts can change his power level by a very large degree.

I think we are supposed to assume that Anakin was hindered (emotionally) while fighting Obi from the previous events that had happened rather than Obi receiving some kind of massive power boost. Gillard stated that Obi knew how Anakin was going to behave before the fight happened.

From Lucas: “Difference between the two characters is that Obi-Wan is more experienced but Anakin is more powerful.”
 
Anakin wasn’t hindered nor is Kenobi any different from the start of the movie. It was his superior power vs Kenobi’s superior experience. Experience won in the end.

As for the Anakin being hindered. I don’t think anyone can deny he was reluctant to fight him. I mean even after he thought his suspensions of Kenobi having an affair with his wife was confirmed he still gave him a chance to walk away. The obvious problem with that argument is though is Kenobi’s own obvious reluctance something Gillard brings up several times. He certainly wasn’t fired up with righteous conviction. In any case Anakin wasn’t pulling any punches, he was channeling his rage effectively,  and the JN affirms the very anguish he felt strengthened him not hinder him. 
 
As for KF comparisons.  We hardly see KF Vader in action. I know I say this a lot but he’s one of those characters alongside  RotJ Vader and “EnOfRotS Kenobi” who’s achieved an unjustified mythological status. What has he done that really puts him above Mustafar Vader who is confirmed to be more powerful?  Killing featless Jocasta Nu and Drallig? Maybe just maybe Kenobi is better than them? Besides he needed some time to dispatch Serra and Ti survived an encounter. This guy isn’t the Sidious + tier opponent the community makes him out. 

People bring up the dragon but I would argue the venomous bite proves that the dragon never truly left him to begin with. Besides he knows how to convert the fear born from the dragon  into anger for power, as AZ pointed out it’s exactly what he did on IH; drawing on negative memories from his childhood and losses and making it his strength which goes hand in hand with the JN depiction of Anakin drawing strength from his anguish.

We need more Bane wank.