All out? I'd have to believe that Sidious' lightning will incapacitate Vader(if not kill him), so it would really end up being Sidious vs. Dooku. I'm not sure if Sidious has picked up a blade since ROTS but it's clear that his force abilities have increased by a considerable margin. With that said, Sidious should be able to keep his distance from Dooku's lightsaber, and get the victory.
Why wouldn't Vader be able to block Sidious lightning with his saber as Mace did in ROTS who was very close to Sidious when he unleashed his force lightning?
While Vader is extremely powerful, physically, he lacks the advantage of Vaapad, which is what allowed Mace to not block but deflect the lightning back at Palpatine; it's not as though the bolts were just hitting the lightsaber and couldn't break through, Mace was sending them back. But if the novelization is any indication, the sheer force of Palpatine's bolts were pushing the lightsaber back upon Mace to the point that he was "choking on ozone."
And, lest we forget, Sidious had enough energy to continue. Mace was on the verge of exhaustion.
But there are alternatives: Palpatine could disable Vader via telekinesis, disarm him via telekinesis, give him a thrashing ala Starkiller. Or it's very possible -- given Palpatine's performance in Betrayal -- that he could generate such a storm of lightning that Vader couldn't possibly channel it all into his lightsaber.
Nice answer, I thought Mace was just blocking the attack not deflecting. Since I want to make this a match I will mention this, Vader even though he die was able to do a Kamikaze move on Sidious. Perhaps he could do so again.
Next speculation question is that Yoda was able to block the lightning with his hands due his power in the force, is it a long shot to say that Vader saber might be able to withstand the force lightning due to Vader's strength in the force?
I think it has more to do with knowledge in the force than actual power, knowledge that Vader doesn't possess. And again, Mace could hardly contain it using Vaapad so Vader stands little chance.
I guess the only thing I can add is can Sidious take out Vader quickly enough that Dooku does not be a dangerous distraction. When Sidious decided to used his lightning on Luke to kill him he did not die immediately neither did Vader when he kamikaze.
Sidious would kill Vader ina picosecond, because he has uber lightning as he burned plasteel with one hand.............. Dooku would get a few more feet towards him, but Vader is more powerful than Dooku and Sidious is more powerful than Vader.............
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Sidious electrocutes Vader. Vader dies. Sidious electrocutes Dooku. Dooku dies.
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pretty much what i was saying.............. but you cannot deny that Vader is morepowerful than Dooku. And Sidious is the most powerful sith to ever exist, Vader suprised him to kill him.
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Nanye i ne Anduril i macil Elendilo
Lercuvanten i moli Mordoreo
Isil
Turgon aran Gondolin tortha gar a matha, i vegil Glamdring gud dae lo, dam an Glamhoth.
Count Dooku beats everyone. Except Revan. He can't stand up to Revan's ambiguity. No one can.
__________________ Recently Produced and Distributed Young but High-Ranking Political Figure of Royal Ancestry within the Modern American Town Affectionately Referred To as Bel-Air.
for once, i actually agree with him, as Vader(in his suit)is more powerful than before. Dooku lost to him without his suit.
__________________ Anar
Nanye i ne Anduril i macil Elendilo
Lercuvanten i moli Mordoreo
Isil
Turgon aran Gondolin tortha gar a matha, i vegil Glamdring gud dae lo, dam an Glamhoth.