I think Madara has the advantage since he has EMS + Rinnegan, while Obito just has MS + Rinnegan, but it certainly would be a close battle, at least based on what we have seen so far.
Obito needs to be in close range to suck madara in kamui.
Madara isnt gonna let obito get in close range.
Obito cant win without sucking madara in kamui.
Obito cant win.