I am inclined to say that Sids still might win in terms of sabers. While Vader becomes much weaker at lightsaber combat from ROTS to ROTJ, Sids is still probably the same, or maybe a bit weaker. This is due to the fact that Sids hasn't undergone anything, and age is not a factor. And ROTS Sids took on Yoda and tied (even though I would say Yoda could have won had he not fallen), while I think ROTS Anakin would lose to the wise Jedi Master.
There is a book where the Emperor, after Vader disagrees with him, takes a grasp around his neck and prevents him from breathing, taking him to his knees. Palpatine would take this easy.
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Lightsaber skills don't exist. Only midicholorean count explain all wich is basically like the powerlevels. Vader is 80% of Sidious' powerlevel so that will tell you all.
And Darth Vader is a very bad fighter anyway because he didn't learn further after he got teh suit and can't even keep up his arms anymore.
Bull crap, in Dark Lord: the rise of Darth Vader , vader demonstrates some pretty impressive abilities, and if palpatine choked vader to his knees, its because vader let him, Vader could of caved palpys skull in with his fist for Gods sake.