It’s an interesting fight.
It’s made quite clear that Ahsoka was Vader’s equal in their fight.
It was probably Vader’s use of his adapted lightsabre form which was designed to combat baseline users of Ataru, such as Ahsoka. Ahsoka made short work of fifth brother and seventh sister, even defeating sixth brother without a lightsabre and only with her use of the force.
Maul on the other hand was a raging beast.
He handled Qui-Gon and Obi-Wan in TPM with ease and would have defeated both of them in a normal duel. His force use was minimal and only applied in a few situations.
His returned self in TCW was rage amped and debatably even stronger than his TPM version. His use of a single sabre and dual sabres was top notch and he was only beaten by bloody Sidious and Kenobi, who was a tank in his prime and on a level with Vader.
I think they are equally competent with the lightsabre, Ahsoka’s force application is better, but only because Maul scarcely employed it and doesn’t have many showings.
So this battle could go either way. In canon it is super close. I go with Ahsoka, but she would be bruised and injured everywhere, possibly even losing one of her lightsabres. Maul in Legends is even stronger, so I go with him, just as exhausted as Ahsoka in their canon fight.
Let’s see how their fight in TCW this month plays out!