plz let's be clear what chakra quality really is, let's see what wiki says about the elder son
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'he inherited the sage's "eyes"
powerful chakra and spiritual energy'.
^^ Sasuke clearly out classes naruto in chakra quality, been a descendant of the elder son means possessing power chakra closer to the sage's power chakra and that was further backed up by the nine tails saying sasuke's chakra was even more sinister than even his own... And if naruto's chakra quality was even closer to sasuke's the nine tails would've said so, so that's completely out of the question.
The logic is quite simple here, i thought we've been through this before that chakra quantity doesn't decide the penetrating power of a technique?? Just read my earlier post again. FRS is just a combination of wind and shape manipulated chakra into microscopic needles while susanoo is actually a materialisation of the powerful chakra... Now saying FRS can destroy a huge mass of chakra with such quality(susanoo) is like saying, "hundreds of clay sands and small stones can shatter a house built with diamonds".