I agree with Draco. Obito was portrayed above Kabuto even without the Rinnegan. He was confident to take him out even with the Edo Akatsuki as a support, with Kabuto ressorting to use edo Madara as an extra-measure to have Obito on his side
And even later, Obito's only problem was Edo Madara when he came to ask him how to stop edo tensei, with him thinking it would be simple to control Kabuto with genjutsu and undoing the jutsu
And by feats, Obito's phasing counters all of Kabuto's arsenal(white rage, tayuya's genjutsu, …), his juubi size katons would also overpower the rest of Kabuto's ninjutsu with him also having suiton, doton and mokuton suppression at his disposal, with his skills displayed against KCM Naruto, Bee, Kakashi(counter to his kamui) and Gai ultimately showing he shouldn't have problems maneuvring around and absorb Kabuto into the box land.
As an extra-measure, he even has a 10minutes long Izanagi that Kabuto should have no knowledge about(since he didn't know Izanami) that he could use as a support for a swift win
With the Rinnegan, it'd be easier with the gedo mazo's destructive force, outer-path mentioned to be stronger than Nagato's, human path that he mentioned he could have used on Yamato, but would kill him.