Korto Vos
[:::::{============)
Well Saruman and Sauron are both Maiars, or demi-gods. Technically, they should be extremely powerful. Sauron is able to cut down entire battalions of men and elves at the Battle of Dagorlad at the beginning of Jackson's FOTR. Saruman fires destructive thunderbolts in Ralph Bakshi's film adaptation and a fireball in the extended edition of Jackson's ROTK; he also controls the weather in Jackson's FOTR. Since Sauron is the most powerful of the Maiar, it isn't unreasonable to conclude he has access to stronger versions of these powers. In addition, the Witch King demonstrates the power to shatter items (such as Gandalf's staff) [though this crap doesn't occur in the book], and burn weaponry. If Sauron bestowed this power to the Witch King, it's evident he has these skills as well.
AND Sauron only "lost" to Isildur because he bound most of his powers into the One Ring, and when that was removed from his body, he was only left as a spirit.
Are we assuming that Sauron is at full strength but doesn't have to worry about Yoda chopping off his finger or Force Pull-ing away the ring?
Anyway, that being said, if Yoda can beat Voldemort (haha Quan 😉 ), and Obi-Wan also has strong precognition and speed, who knows how this duel would turn out?