Ben Kenobi has deepened his connection to the force:

"Obi-Wan is very likely doing a lot of meditating on the force and he's likely deepening himself and he's learning those techniques Qui-Gon was exploring"(Henry Gilroy)

Twin Suns Rebels Recon

Ben Kenobi has improved as a duelist:

Andi Gutierrez: "The actual duel between the two Masters is very short, like a samurai film. How did you come to the conclusion that it had to be done this way?"

Dave Filoni: "If you talk to a lot of people that sword fight, they'll tell you people that are very good don't have long fights. It's very quick. And so that scene, it's an homage to the Seventh Samurai. I think on one level people would be excited to see another prolonged lightsaber fight but I just never really saw the confrontation that way because to do that is to say the character's don't have growth. Yes, it's exciting as an audience member but it's not a really believable thing. The story telling has to evolve."

Source: Twin Suns Rebels Recon

Maul tries to get Obi-Wan with a very similar move as he gets Qui-Gon. Which is he blocks and uses the blunt of his hilt to smack Qui-Gon in the face. So I had Maul try to do the same thing to Obi-Wan but again, to show growth, Obi-Wan is ready for that and slices it right in half.

Ben Kenobi has become a "very good" swordsman compared to his prior incarnations indicating his superiority:

Andi Gutierrez: "The actual duel between the two Masters is very short, like a samurai film. How did you come to the conclusion that it had to be done this way?"

Dave Filoni: "If you talk to a lot of people that sword fight, they'll tell you people that are very good don't have long fights. It's very quick. And so that scene, it's an homage to the Seventh Samurai. I think on one level people would be excited to see another prolonged lightsaber fight but I just never really saw the confrontation that way because to do that is to say the character's don't have growth. Yes, it's exciting as an audience member but it's not a really believable thing. The story telling has to evolve."

Source: Twin Suns Rebels Recon

Kenobi has grown as a character and has become enlightened consequently becoming more powerful:

Filoni explained, however, that “power” means different things to different people. For the Sith it’s literal, but for the Jedi, it’s about selflessness and sacrificing to help others. “

http://io9.gizmodo.com/the-producer-of-star-wars-rebels-on-tonights-incredible-1793376931

“It really is to express the difference between the Jedi and the Sith. Which is the Jedi become selfless and the Sith remain selfish. When pressed, because Obi-Wan is protecting someone else in the end, he does fight. But because he is so true and knows who he is in that moment, you can’t defeat that. So Obi-Wan is going to strike down Maul because Maul is such a broken and lost person, which I think is why in the end you see Maul being cradled by Obi-Wan.''

- http://io9.gizmodo.com/the-producer-of-star-wars-rebels-on-tonights-incredible-1793376931

Kenobi is indicated to be a master swordsman:

Filoni said the inspiration for the fight was Kyuzo, the master swordsman in Akira Kurosawa’s Seven

--- http://io9.gizmodo.com/the-producer-of-star-wars-rebels-on-tonights-incredible-1793376931

Kenobi has surpassed Maul:

" I felt that with Maul, any moment that he parries Obi-Wan is saying that he’s as good as Obi-Wan and I don’t think that’s true. I don’t think Maul ever accepted a path of selflessness and enlightenment and in the end, never getting over his need for revenge, and his anger and the way his life worked out is what undid him."

--- http://uk.ign.com/articles/2017/03/...orylines?page=3

“It really is to express the difference between the Jedi and the Sith. Which is the Jedi become selfless and the Sith remain selfish. When pressed, because Obi-Wan is protecting someone else in the end, he does fight. But because he is so true and knows who he is in that moment, you can’t defeat that. So Obi-Wan is going to strike down Maul because Maul is such a broken and lost person, which I think is why in the end you see Maul being cradled by Obi-Wan.''

- http://io9.gizmodo.com/the-producer-of-star-wars-rebels-on-tonights-incredible-1793376931

Kenobi is superior to Qui-Gon

Maul tries to get Obi-Wan with a very similar move as he gets Qui-Gon. Which is he blocks and uses the blunt of his hilt to smack Qui-Gon in the face. So I had Maul try to do the same thing to Obi-Wan but again, to show growth, Obi-Wan is ready for that and slices it right in half.

--- http://io9.gizmodo.com/the-producer-of-star-wars-rebels-on-tonights-incredible-1793376931

Maul feels Kenobi's presence from across Tatooine:

https://youtu.be/A_6Z630T-hY?t=19s

Kenobi's presence on the death star causes "a tremor in the force" which Vader can feel:

https://youtu.be/k0GNAJwxTnQ?t=1m33s

A. Strength:

Ben briefly tussles with Vader in a blade lock before his blade is thrown back:

https://youtu.be/sq51w34Hg9I?t=34s

Parries and blocks multiple strikes from Vader:

https://youtu.be/sq51w34Hg9I?t=32s

B. Speed/Agility

Is able to react to and adapt to Maul's attacks:

https://youtu.be/69_xYPQ42Rg?t=1m43s

Jumps over a wookie+his boulder and swings his blade before he can slam ben with a rock:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#15

Moves around Vader:

https://youtu.be/sq51w34Hg9I?t=44s

Dodges one of Vader's attacks:

https://youtu.be/sq51w34Hg9I?t=46s

C. Durability/Pain Tolerance

Is choked and thrown down by a wookie without noticable physical harm:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#12

Uses the force while being electrocuted:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#13

Tanks a hit from an electric sword:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#16

Has no visible harm despite being blindsided and whacked in the head by a wookie:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#17

A. Telekinesis

Telekinetically writes down a story about Yoda while meditating and lifting small rocks many years pre-prime:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-27?id=102231#3

Telekinetically throws many small rocks while being shocked many years pre-prime:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#13

Telekinetically breaks up rocks into smaller segments while being shocked many years pre-prime:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#14

Telekinetically pulls lightsaber while shocked many years pre-prime:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#14

Telekinetically throws down multiple large boulders many years pre-prime:

http://readcomiconline.to/Comic/Star-Wars-2015/Issue-20?id=63617#14

B. Sense

Senses Alderaan's destruction:

https://www.youtube.com/watch?v=EKu7TYWNxqA

Kenobi was able to sense Maul was looking for him:

https://youtu.be/u-0gmL2ecyg?t=1m35s

C. Telepathy

Kenobi uses a jedi mind trick on storm troopers:

https://youtu.be/532j-186xEQ?t=40s

D. Force Mimicry

Ben Kenobi mimics a Krayt Dragon:

https://youtu.be/s4UhQ4hZzRM?t=1m52s

Ben Kenobi imitates a sound to distract storm troopers:

https://youtu.be/k0GNAJwxTnQ?t=3m29s

E. Immortality

Kenobi has learnt how to transcend the physical plane from Qui-gon:

"Obi-Wan is very likely doing a lot of meditating on the force and he's likely deepening himself and he's learning those techniques Qui-Gon was exploring"(Henry Gilroy)

Twin Suns Rebels Recon

Kenobi transcends the physical plane as a force ghost upon death:

https://youtu.be/sq51w34Hg9I?t=2m13s

Kenobi talks to Luke as a force ghost:

https://youtu.be/Z8uDQuWlnww?t=46s

Kenobi decisively beats Maul in a shorter samurai style fight:

https://youtu.be/jeG215-yu-k?t=1m4s

Kenobi fights evenly with Vader before voluntarily conceding the bout:

https://youtu.be/sq51w34Hg9I?t=32s

http://www.starwars.com/films/star-wars-episode-4-a-new-hope-story-gallery