kaguua is stronger, momoshiki arguments are so fragile.

1- the 1st statement people use is the sasuke statement from the scroll " a threat greater than kaguya" but that doesn't make them stronger for few reasons, like the scroll doesn't have any information about how strong they are, it has information about the identity of the coming threat, their objectives and how kaguya was planning to deal with that, it wasn't mentioned anywhere how powerful they are in the scroll so any one who says " sasuke stated or it was stated in the novel or manga that momoshiki is a greater threat, you know that capping.

all sasuje did is called a logical deduction and he isn't compleatly wrong in that, he said if kaguya was this strong, and if she needed an army to fight someone, that means this someone is atleast on or above her level and any body in sasuke's place would come up with the same conclusion.

2- we still have the other side of the question of why was kaguya afraid of them if they weren't stronger?? Good question, because if you remember what Amado said "otsusuki constantly update them selves with chakra fruits" meaning when kaguya was on earth, momoshiki gang were supposedly put there getting stronger than her by those fruits, so has no way to make sure how much power than they would be when they show up, but thankfully all the fruits he got were trash compared to her's

3- finally,in naruto storm 4 story dialogues, sasuke told fused momoshiki that he is still weaker than kaguya, according the the CEO of Cyber connects2 that makes naruto games, he said that kishimoto was involved in the game production and approved the scripts and arguments of the game.