Originally posted by Ziggystardust
It is true, yes it is, that Maul's statement doesn't have to be taken at absolute face value and heralded as some undeniable fact. But even if we are sticking by it with one-hundred percent certainty, the statement is that Maul can not defeat Vader without help. That by itself doesn't preclude the idea of a stalemate or some prolonged death-match with a bloodied an bruised winner emerging from the fray. Vader vs Maul is hardly set in stone just yet, and until it's displayed on screen, it will always be a debate.
We don't HAVE TO take Maul's statement at face value, but it would be pretty uncharacteristic for Maul to admit that if he had a shot. I don't ever remember him saying any such thing about Obi-Wan Kenobi or Count Dooku.
Then there's the fact that the people he was trying to convince bought that part of his argument at least. No one was like "I don't buy his reasoning. He wouldn't be afraid to challenge Vader."
Now bear in mind he didn't try to manipulate them by saying "I can not defeat the Sith alone" or "I can not defeat the Empire alone," but specifically "I can not defeat Vader alone", which they all completely bought. And when asked about that line Sam Witwer and FPJ talked about how Protective Filoni is of Vader.
As for Filoni, he confirmed that the initial plan was for Maul to die to Vader in that episode, but they ultimately decided they wanted Maul around a little longer.
Then there's their respective fights on the show. Where Maul was stalemating Ahsoka, Vader was soundly defeating Ahsoka. Where Vader handles Kanan easily one handed and has him and Ezra running for their lives, Kanan, while blind defeats Maul 1 v 1.
Now yes he was obviously stretching through the Force to protect Ezra. Probably stretching beyond his means given how he falls right after defeating Maul. But the show's made it pretty clear there's no way Kanan could even challenge Vader, let alone defeat him.
So bearing all that in mind, I think we can safely take Maul's word for it that he can't defeat Vader alone.
As for a near stalemate, or a prolonged death match, that would be my preference, but going by the above evidence, I think it would be more of a Vader vs Ahsoka type fight.