You overestimate him too much, they both have the bijuus power and one has full Kurama and Naruto has experience against the Rinnegan
And Naruto has the advantage of of having the superior RSM because of his Ashura lineage.
You are wrong
Naruto=Half Kurama(yin)+small part of Yang Kurama+small part of other 8 beasts chakra.
cant be compared to
Madara=Half Kurama(yang)+full chakra of other 8 beasts.
Juubi although Madara said it slowly gained his former power still below Prime Juubi(below)
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Missing big chunk of remaining chakra(Kurama and Gyuuki) still effected Juubi form and power. Small chakra that Juubi got from Kin and Gin bro and also Gyuuki part is not enough.
Thats mean what I want to tell you here is, RSM Naruto with all tailed beast chakra he got still cant matched Juubi chakra inside Madara.
What help Naruto matched Madara and Kaguya power is Hagoromo chakra plus his chakra and tailed beasts. Without Hagoromo chakra but only his own chakra+tailed beast chakra, no way he can matched JJ Madara even though his Arsenal is on different level.
He need
massive chakra to perform all that large scale attack that logically his own chakra+Half Kurama chakra and small part of other tailed beasts chakra unable to give.
Unless he absorb all Natural energy circulating the earth that sure different games altogether.
