Revan is very knowledgeable and very strong in the Force, but Sion has the power of Immortality. Revan uses strategies and techniques, but Sion has strength and power. If Revan followed the path of the Light Side he would be able to persuade Sion to let go of his power of Immortality and die, but if Revan followed the path of the Dark Side he would not care and fight until he dies. Basically, none of them will win, but that is just my opinion.
There is no emotion; there is peace.
There is no ignorance; there is knowledge.
There is no passion; there is serenity.
There is no death; there is the Force.