Because he would be pressuring them via PS slashes, and if the barrier drop doesn't happen prior to the destruction of the CT meteors, Juubito preps the tree, and Madara pressures them while it is happening. Though Naruto can destroy the tree with a single elemental RS, Juubito with Madara's Limbo clones would also be pressuring Naruto's during it's charge time.
Madara pressuring them doesn't mean they won't be able to form a Bijuu Dama. Not to mention they can fuse their Avatars together like they did against Juubito.
If Juubito preps the Bijuu Dama tree and the barrier, then once the Bijuu Dama fire, Sasuke warps away and Naruto tanks them with the Gudo Dama, Madara better do the same if he doesn't want to die. If he does keep attacking Naruto despite the barrier, then Naruto has clones hold off Madara and his Limbo while he, the original, sits back and tanks Obito's Bijuu Dama.
Like I said I have no feats to substantiate my claim.
Eh, I'm not going to debate this, many variables and it's not exactly easy to decide.
Alright.
Though, like I said, an unrestricted Juubito and Madara would most likely win mid difficulty. Juubito would actually use the Rinnegan and the Sword of Nunoboko, while "technically featless" was said to be immensely powerful and this time Obito's will won't change this. He can also let the Juubi out, which would tank everything. Just so many variables/ways this can go down.
The only Rinnegan jutsu Obito can use is Human Path and Outer Path until implied otherwise. Sword of Nunboko was destroyed by Sasuke and Naruto's first Avatar fusion. They destroy it again. Where was it said that the will of the user determines the strength of the blade.
The Juubi won't tank BDRS, which carries the properties of the Gudo Dama, Bijuu Dama and Rasen Shuriken. The Gudo Dama is like Jinton, as stated before, and its magnified to Bijuu Dama's scale when used with BDRS. Juubi would get vaporized.
