In a bout of physical strength, it's blatantly obvious that Madara would triumph over Obito. However, Obito doesn't fight in a way that pits brute strength against brute strength. In fact, someone like Madara who DOES fight by using brute strength, it'd put him at a slight disadvantage.
What I mean is that, unless Kakashi was helping Madara fight, Madara would have a difficult time even touching Obito through Kamui. The ability to hurl down meteors and destroy geography is a mute point. While on the other hand; Obito touches Madara even once and he'd be stuck in Obito's pocket dimension.
Obito isn't stronger, but he's water to Madara's fire.
Obito fought Kakashi, Naruto, Killer Bee and Guy at once, the only reason he even took damage was because of Kakashi holding his eye.
Now, as far as we've seen, Madara does not have Obito's space/time jutsu; Kamui. He has the same type of MS that Itachi and Sasuke have. I say this because Itachi says that "if an Uchiha with the ability to awaken the Mangekyo holds Amaterasu in one eye and Tsukiyomi in the other, they will achieve Susano'o." So one can assume that Madara does not have the ability to cancel Obito's Kamui.
Obito w/no Kamui <<<<<<<<<<<<<<<< Madara
Obito w/ Kamui > Madara
This verdict is reached simply because the way Obito fights is different then Madara's.
Tell me what you think; I'm curious how people think Madara would get around Kamui alone.