Since the starting distance is 100 meters, it's easy to assume that lightsabers will not be used at any point during this fight. IIRC there were no quotes about Sheev being the "strongest Sith who ever lived" by the time of TPM, other than the claims he made himself. It's foolish to take them at face value, given that he said these things in the heat of an intense moment (his killing of Plagueis). There's no reason for us to believe this claim, given that it is from a Sith who was proud that he had succeeded in killing his master. It's clear he was gloating, not making an educated statement. The only time we have real concrete statements of his being the greatest Sith ever come around RoTS, from reliable/credible sources. By this logic we can dismiss the "greatest Sith ever" wank.
The best feats we have for Sidious at this point are his small battles in the Plagueis novel, and having been stated to have surpassed his master. In Force only, I have Plagueis in the same tier as SoR Revan, who has been stated to be solidly inferior to Vitiate before the events of Ziost (granted this was only by days). Additionally, with regards to Force prowess, the Dread Masters are collectively comparable to Plagueis (still inferior, but not by a huge margin). Said Dread Masters were said to be "insignificant compared to the Emperor." We can draw from this that Plagueis is very noticeably below Vitiate. Logically speaking, we have no evidence that supports or reason to believe Sidious being as far above Plagueis. As a result, we can deduce that Vitiate is superior to Sidious as of TPM.
For those (like myself) who don't like going by statements alone, here are some feats for Vitiate that are superior to all of Sidious' own by this point. His domination of Revan (after actually taking the fight seriously) is a good example. Another is his complete domination of the strike team of HoT, Tol Braga, and others completely effortlessly. Sheev has done nothing of this level by TPM.
I'm not even going to bother getting into DE and Valkorion. That goes back and forth endlessly, but in this case there's really no arguing that DE can take out Valky before Vitiate overwhelms TPM Sheev.