1v1 it would easily be Vader. He can see Sauron's attacks before they happen, he can move any object (including sauron himself) with the force, and he has a lightsaber.
Step 1) rip Sauron's weapon out of his hand with the force
Step 2) cut off Sauron's hand
Now after this fight is where Vader would probly fail. Vader, being easily tempted by power, would most likely keep the ring instead of destroying it, which would get him in the long run.