This is strictly dueling abilities. In canon, it is a fact that Vader's powers grew as time proggressed well beyond Anakin after rots.
However, in canon I believe Vader is also superior to Anakin in sabers. We 100% know Vader is a superior duelist than Palpatine. I don't think we can factually say the same for Anakin. We know he's more skilled than Dooku, and he's stated to be more powerful than Dooku by Palpatine himself.
I'd say in canon saber skill rank goes Luke > Vader > Mace > Palp > Yoda > Anakin > Dooku