Kaguya and naruto can fly. Sasuke can only fly with PS, so he needs it in order to fight solo while in the air, unless naruto lends him a hoverboard.
PS also was able to fight kaguya while obito gave his final speech, and we saw kaguya had to dodge the slash in the last chapter. Not only that, but susanoo would probably make sasuke immune to kaguya's bone ash technique, so I think he should still use it. At best, I think he should try and make his PS as small as possible to conserve chakra.
Naruto didn't even sustain noticeable damage after taking multiple chakra punches from kaguya though...
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