Originally Answered: In Legends did Sidious value Dooku more then Maul? The answer is no. Dooku is, and always has been, a pawn of Sidious to be used and discarded. Maul was Sidious' personal apprentice whom he trained for years, honing him into the perfect sith weapon of rage and dark side energy.
Indeed, Palpatine seems to have seen Maul as an ideal apprentice, admitting he was "a loss" compared to Dooku in Darth Vader #20.
Palpatine Never Truly Thought Highly Of Darth Maul
But Palpatine also believed that all who used the Dark Side of the Force would also feed directly into his own power - and Maul was nothing if not powered by pure anger (he was practically raised by birth to hate the Jedi Order).
Sidious would have no doubt sensed Maul's potential power as the son of Talzin, a noted powerful practitioner of dark magic. It is because of this that he opted to abduct the young Maul.
The movies establish a pretty definitive gap between the 2 of them. While Maul becomes stronger after his return, there is no indication he ever surpassed Dooku. People use false evidence to say that Maul is 'confirmed' to be stronger.
Darth Maul
Dooku despises Maul for being a threat to him, and for killing his beloved padawan Qui-Gon, and Maul hated Dooku for being his replacement. They also didn't regard each other as a true Sith: Dooku saw Maul as nothing more than a trained animal and Maul saw Dooku as a Sith pretender.
By his singular hatred for Kenobi, Maul survived though at the cost of his sanity (which was later restored by Mother Talzin) and he surfaced many years later to exact revenge on Kenobi.
Darth Maul and Obi-Wan's long-standing rivalry started in Episode 1 and lasted all the way until Star Wars: Rebels. Throughout his lifetime, Maul seemed to hate Kenobi! Every time Maul says Kenobi.
He fell under the influence of Supreme Chancellor Palpatine of Naboo, and left the Jedi Order. After learning that Palpatine was secretly the Sith Lord Darth Sidious, Dooku turned to the dark side and became a Dark Lord of the Sith himself, replacing Darth Maul as Sidious's second apprentice.
With his master, Darth Maul hoped to destroy the Jedi and restore the Sith to galactic power. However, Maul's hatred of the Jedi was more personal. He was filled with anger when he realized that as a child, the Jedi had not come for him.
Once his sanity was restored and Maul was told about the war, he wasn't surprised. He knew it was his Master's plan. Obviously, Sidious never planned for Maul to die, unlike with Tyranus.
If Maul knew, he would have tole Obi Wan or another Jedi during the Clone Wars. Dooku knew Palpatine was Sidious as he told Obi-Wan about him controlling the senate and referred to him as the dark lord. There's no real way of actually knowing if he knew ab palpatine.
Darth Maul might have surpassed Darth Sidious if he did continued his training and absorbed all the knowledge and arcana of his master. “But the boy… the boy has inherited your talents… and so much more. You have done well to provide me with such a remarkable candidate. Your dedication will not be forgotten.
With Obi-wan he is very cordial and even complementary at times, but when he is dealing with Anakin he clearly treats him with contempt.
Anakin gives in to his hatred of Dooku and uses his anger to overpower him, severing both of Dooku's hands and leaving him helpless. Palpatine then orders Anakin to execute Dooku on the spot, thus betraying Tyranus. After initial hesitation, Anakin decapitates Dooku, much to his horror of the betrayal by his master.
He ignites his new double-bladed lightsaber and engages Obi-Wan in a duel, but Obi-Wan again bests him in combat, cutting off his opponent's horns. Maul is killed by a blaster bolt to the head from Owen Lars. Obi-Wan thanks Owen, and says he will take Maul's body into the desert and burn it.
The young Jedi, in a surprising move, cut Maul in two and sent him tumbling down the planet core, seemingly destroyed. Thought dead, Darth Maul survived his injuries by focusing on his hatred of Obi-Wan Kenobi, the Jedi who cut him in half.
A: While Maul's initial hatred towards Kenobi stems from the death of Qui-Gon Jinn, his master, it evolves into a personal vendetta against Kenobi. Maul's pursuit of revenge is driven by his own desire for power and dominance rather than being solely rooted in Sith ideology.
Maul once tried to turn Ahsoka to the Dark Side, but failed. Maul calls her "Lady Tano" to mock her.
Maul may have developed a slight fondness for Ezra and still used Ezra to achieve his own goals, it did appear that Maul genuinely wanted Ezra as his apprentice. However, it is made clear by Sam Witwer that Maul does want Ezra as a replacement for his dead brother.
During his exile, Maul's mind was shattered. He became obsessed with revenge, fueled and kept alive only by his hatred for Obi-Wan, despite losing his mind and many memories. His aggression and fear increased in his crazed condition, as Maul attacked Savage when he first encountered his brother on Lotho Minor.
The count bested both Jedi in their duel, using the power of the dark side and taking advantage of young Skywalker's impetuous nature. But before he could land a killing blow, Master Yoda entered the fray. Not even Dooku's Sith-enhanced powers were enough for him to defeat Yoda.
That notwithstanding, Master Windu was also one of the best. If the two spared as Jedi, Dooku would probably win the match because he was the better all-around duelist.
Dooku could have not beaten Yoda in Geonosis, meaning that the fight would have ended with Dooku either killed or captured had it continued. At that point, the only two Force-sensitive warriors who could beat Yoda in a fight were Mace Windu and Darth Sidious.