Two near equals for the apprentice of the most powerful sith in history face off against the most powerful force user in history up until Sidious himself
Challenging someone doesn't really make you an equal or near equal. Near equal implies that you'd be capable of taking rounds out of 10, maybe even up to 5 (but more like 2-3). Do you honestly think Ahsoka or Ben are beating Vader 3-5 times out of 10 fights? If so, why?
Also wasn't Ben being pretty quickly overwhelmed by Vader in their ANH fight? Sure he was sort of holding his own, but it's not like he had a chance at winning from what I've heard about the supplementary material (i.e. not the movie).
Nah, that's easily attributed to malachor being a nexus.
The Fact that Ahsoka was able to contend with vader for almost 2 minutes(50 seconds off screen) and only started clearly being at a clear disadvatage for the last 20 seconds or so on a ds nexus makes me think that on even ground she'd be right below vader and on par with ben tbh.
And I'd argue the nexus is pretty significant given it elevated the inquisitors from being stomped by ahsoka to being able to individually able to hold their own against her.
The DS Nexus which the Story Group can't confirm amplified Maul and Vader in combat.
Even Filoni has made zero mention of any such amp.
So yeah speculation.
Actually Ahsoka's stomping the Inquisitors (off Malachor) was pretty similar to the level at which Maul was stomping them (on Malachor), hence further evidence Maul and Ahsoka are approx on par.
Ahsoka solos. She tanked a Force Push from Vader and even landed one on him. Let me just remind you how Vader practically one-shoted Yoda's equal, Sidious, with a Force Wave: (please log in to view the image)
Add to that Ahsoka didn't get incapacitated by Sidious' lightning as per Filoni, whereas Yoda did... And it's clear that Ahsoka solos.