Sidious, beat the Zabrak bros with ease, carved up 3 Council members in seconds; did the same thing after the formation of the Empire where he cut down several Jedi with one swipe in his throne room, in the novel Lords of the Sith, Vader was taken aback and amazed and the speed and dexterity with which Sidious dispatched the Lyle nest and that was all well before his prime power
Where is Vader confirmed to be a better lightsaber duelist than Palpatine in canon? Not that stupid magazine that lists "5 red lightsaber wielders", surely?
Well, for starters it's a book. And a book that is published as official canon. You don't have to like it, but it doesn't change the fact that it's true.
By no means am I saying Vader would stomp Sidious in an all out. He's just the greater duelist. Unless there's something new that contradicts this.
Unless ESB Palpatines Saber skills have gone to complete shit, he would win. All that power in the force will enhance his speed and strength to stupid levels.
Also I like how everyone likes quoting the top 5 red duelists as proof that Vader is better than Sidious in Sabers, but none of those same people take it as fact that Maul would best Dooku in Sabers, or heck even Ventress beat Kylo. I would personally be perfectly happy with that list, but its funny how people pick and choose.
The Tweet you posted is dubious, though: "I believe"... "To my recollection." Certainly doesn't come off as authoritative by any stretch.
I know people like to go the Tweet route for things like this, but even Matt Martin has said on more than one occasion that Tweets are not canonical in and of themselves -- published material always takes precedence: https://i.imgur.com/jeFfjrT.jpeg https://i.imgur.com/2N8lfor.jpg
That said, the list also says "Top 5 red lightsaber wielders", followed by each character receiving a specific numerical entry, from 1-5. Doesn't seem like the placements were meant to be 'randomized' to me. /shrug
But if you choose not to believe that, I get it. You're certainly not the first person who has ever disagreed with the order.