Vader both rounds.
In canon, Vader is more powerful than Anakin, has a greater baseline physicality, and more technical skill.
In Legends, Vader has already regained a lot of his former physicality by even 18BBY (as of 18 BBY he's noticeably faster than 1 year-post ROTS Kenobi), an at least comparable command of the Force to Anakin (given his greater TK) he has a greater baseline physical strength, he has more developed lightsaber skill, his fighting style stacks up even better against Dooku now since he also incorporates Makashi, and he has much greater durability and stamina. Granted, he's not gonna be smashing through Dooku like Zonakin, but he'd overcome the Count.