I realy don't get the arguments some people throw in here.
I will leave a "human" Vader out of this since it's obviously that he would be the most powerful of them all.
About the "Cyborg Vader":
You have to keep in mind that there are at least 20 years between the OT and the PT - the "new" characters have better special effects, better stuntcoordination, better training behind them. Imagine ROTJ Palpatine doing what ROTS Sidious did or how the lightsaber duels in the OT would have looked if they had the same technology available they had for the PT.
Still we have a statement from Lucas that Vader in his suit is about 80 % as powerful as Sidious himself. Now have a look at the things Sidious did in ROTS. Killing three Jedi Masters within seconds, giving people like Yoda and Mace good fights. Still OT Vader would be a better swordsman than Sidious because of having more expirience with that weapon. And yes...he lost a lot of his potential when Obi-Wan defeated him but that doesn't actually mean he realy got weaker compared to pre suit Vader because Anakins powers weren't nowhere near "fully developed" in ROTS - take a look at the things NJO Luke can do and that's about 50-75 % of the things a full developed Anakin could have done.
Still OT Vader was able to carry Palpatine through the throne room on the second death star and he throw him into the core while Palpatine unleashed his force lightning on Vader.
And for his lightsaber skill: Sure it looks stupid and slow because they couldn't do that better in the 1970s. Compare ROTS Obi-Wan to ANH Obi-Wan...normaly ANH Obi-Wan had to be as fast as Dooku was in ROTS (even faster because he is younger) - he is not. See...just lack of special effects.
Anakin was powerful with a lightsaber. Vader in suit would actualy have more physical strength (complete mechanic weapon arm) and (since he mastered form V what he hasn't done in ROTS) he would be a better swordsman. So he would kill Dooku...no doubt about that. And Maul isn't even a factor here.
kill yourself yomi
obi wan was done, he had no weapon and was holding on for dear life. all maul had to do was force push him down or do anything except stand there and wave his lightsaber around and obi wan would have been killed. you just dont like maul so you dont want admit he could do anything in this battle
you have to have some power to do what suited vadar did. i mean look at what suited vadar did at the end of ROTS. they had the special effects to show what vadar could do and they did. he killed padme with just his anger. imagin him using that power in combat. yes you can only imagin becuase the old triligy didn't have the special effects to show that type of power. i mean everybody thaught it was sooo cool special effects when he choked that one dude. everybody was amazed. now days darth vadar unleased so much more power without even trying and we aren't nearly amazed now days. he didn't try to kill all those droids around him , he didn't try to brake the metal things holding his hands down. he didn't try to ( let alone want to) kill someone who was at least 100 miles away( maybe even on an other planet i don't know). why was sidiuos happy when vadar could of done all those powers. i mean he was very powerful. he killed many many many jedi before and after the day order 66 was anouced. he was the chosen one. his power exceeds doku's and mauls by far.