Neither are the body mods which Kabuto blessed Madara (undying body, limitless chakra, youthful appearance + Rinnegan). So i've no idea why you would even bring that up. Who said Madara can just take control of the Mazō whilst Obito is using it? He has the Rinnegan along with the Rikudō blood aswell. Madara can't make Obito turn tangible - the latter can remain evasive for as long as he pleases, especially considering he can use the near-instant (hand seal-less) Shinra Tensei to defend himself during Kamui's cool down period. This match has stalemate written all over it. There is no counter to Obito's defence outside of plot barriers. You cannot give me a scenario where Madara can overcome an Obito who is simply remaining intangible for 5 minutes at a time whilst using Shinra Tensei inbetween, especially considering that he'd have Gedō Mazō w/the Bijuu laying waste to most of Madara's Mokuton jutsu. Perfect Susano'o cannot swing it's sword in Obito's direction for five minutes straight and totally ignore the threat of the Mazō and the Bijuu. Similarly, Obito cannot warp him because Madara can defend with a Shinra Tensei of his own. Obito cannot take his soul with Ningendō because, once again, this requires him to turn tangible - Shinra Tensei would once again negate such a move. Since Madara has an immortal body, Obito has nothing else in his arsenal capable of stopping him. Neither of the two have any reasonable way of actually defeating the other outside of plot barriers.
The fact of the matter is, Madara is the stronger of the two because plot requires it. Madara is Obito's sensei, Obito is Kakashi's parallel, Madara is the closest to Rikudō Sennin etc. These hypothetical battles take place outside the realms of plot. You cannot imply that Madara would defeat Obito just 'because he's Madara' or 'because he's Obito's sensei' or 'because the manga makes him look like the superior of the two'. That's weak logic, since we may aswell declare Naruto to be unbeatable at this very moment.
