Who should they help? The choice was not difficult...
"Defeat Kaguya Otsutsuki first..."
They should deal with the easier one first. Fighting one "monster" was simpler than fighting two.
As for the usual case of the weak resisting the strong... Mizuki's main body plus the four members of Team 7 were the strongest side.
The so-called immortal body, the Ten-Tails' true form, the ancestor of chakra, a true god, and so on—those were merely theoretical immortality. Killing them might be troublesome, but it was not impossible.
Sasuke Uchiha's Mangekyō Sharingan secret technique—Takemikazuchi: Futsunomitama—could directly annihilate the soul. Though it could not completely destroy the Evil God and the Ten-Tails at their source, it could at least keep them from causing trouble for several decades.
As for resurrection after that, that would be another great cycle of the era.
Yukimura's Mangekyō Sharingan secret technique—Izunome—was the same. Its cleansing power was incredibly domineering, and no one could afford to underestimate it.
Attribute restraint was not the problem. The problem was the disparity in strength.
Water and fire restrained each other. Flames could heat water until it vaporized, while water could extinguish a blazing fire.
But the flame of a single match could not boil a kettle of water, and a bucket of water was but a drop in the ocean against a forest fire.
Making those two "monsters" submit was like making a tiger sheath its claws and fangs, then shave off all its fur before skinning it and pulling out its tendons. They had to subdue them first.
Otherwise, Naruto Uzumaki and Sasuke Uchiha could only use Six Paths: Chibaku Tensei to hastily seal them away.
But that would merely postpone a difficult problem.
"Is this really all right? Should we wait until they determine the winner, then defeat the one