The fight against Maul is actually the reason Obi-Wan adopted and mastered the Soresu Form. He was able to see in retrospect all of the failings of Ataru and decided to utilize Soresu instead.
Don't get me wrong, Ataru is great if you have ample room to maneuver. It is why Yoda was one of the fiercest lightsaber duelists of the Order, his small size allowed him to capitalize on even the smallest of open spaces, turning a confined space into his biggest advantage against his larger opponents.
I don't think Soresu would be better against Maul, you can see in TCW he still got *** kicked by the half cyborg Maul, without using double blade lightsaber.