I think that Obi-wan would win because he may not be as fast and stuff but I have always been a storng supporter that people get stronger in the force with age and that Obi-wans strikes look like powerful blows while I hate that in the new series that they look like they are just tapping their blades toghether. Kindove like when Anakin(ROTS) fights Dooku in episode three Dooku is having trouble keeping the physical strenght to block Anakins blows.
Also more support of Obi-wan.
"I see you becoming a much greater Jedi than I" Qui-gon to Obi-wan.
I think that Obi-wan has gained more power per hit and lost a lot of speed, but is still able to block fast hits because of his form three style.
Obi was great and he has seen a lot of combat in his time, but you are comparing a retired marine here who has done nothing for 20 years but sitting at home watching TV to somebody who trained right up to the moment of his dead.
Obi may be very powerful yes, but he needs to get back into the game... and when Qui would suddenly show up at his door step Obi would be in a lot of trouble