let me put it this way, Madara knows Obito and he knows about his Sharingan's special ability yet he wasn't worried about it and still made the recent "don't put me on the same level as someone who took years to gather the Bijuu's" statement.
even Obito blackmailed Madara taking advantage of the situation (Madara being an Edo/needs the Rinnegan/Rinne tensei), never thought about facing the guy in real combat (not that simple).
i think it's safe to assume that Madara can handle Obito's ability otherwise he wouldn't be the master mind/the biggest threat to the Shinobi world U_U which is what the writer has been portraying for some time now.