Keep in mind that these two are the same person. They both have each other's strengths and weaknesses.
Both of them are Form V lightsaber combat specialists. That means it's a very level playing field for both Anakin and Vader. Although, if you were to ask me, Vader might have a significant advantage over his younger Jedi self.
For one thing, after his defeat at the hands of Kenobi on Mustafar, Vader still retained his Form V proficiency. However, he also incorporated moves from the other six lightsaber forms. This is seen in his first lightsaber duel with his son, Luke Skywalker. In the first few seconds of the duel, Vader used a few moves from Form II (Makashi). One of those moves was disarming Luke of his lightsaber.
Meta: It doesn't matter. When you make a thread without specifying the incarnation, it is assumed that each character is operating in their most powerful incarnation.
(Notably, Anakin is an exception since he has access to various power boosts depending on his disposition. In that case, the distinction of lightside/darkside has to be made. Good thread!)
On topic: I think that the Cyborg wins this. There might be an argument to be made about Force usage, but in practice the things we've seen from Vader are much more impressive than from Anakin.
(I'll change my vote and argue if nobody disagrees, but this is the safer option I think.)
I'd go with Vader. The deciding factor for me is vaders intimate knowledge of his past self. Vader would know what weaknesses he could exploit and what to be prepared to defend against. He would know what buttons to push to get anakin to lose focus and mess with his head, and he would know anakins style and tendencys inside and out.
Very true. In a way, Vader was more of a master as a Sith than he was as a Jedi. He was alot wiser in his lightsaber combat strategy, being able to incorporate tactics and moves from the other lightsaber styles, along with his proficient lightsaber form: Djem So.
ROTJ Darth Vader was overwhelmed by bloodlusted Luke. Anakin's mastery of Djem So would be a huge challenge for Vader. Sabers is a definite win for Skywalker. Force would be a narrow win for Vader because of superior mastery, all out is Skywalker.
You are aware that Darth Vader was only overwhelmed by Luke because he goaded Luke into becoming angry, right?
Anyway, after his defeat to Obi-Wan on Mustafar, Vader still retained his mastery of Djem So. However, Vader also managed to incorporate his style with the other six lightsaber combat forms, as seen in his first duel with his son.
Also considering that he's fighting Anakin Skywalker (himself), Vader pretty much knows what he's in for. Unlike Anakin, Vader was more of a master on the Dark Side than he was on the Light Side.