Stronger comes from winning a contest. Obito would beat EMS Madara due to his lack of Intel on Kamui, unless if classified in the match-up, but realistically has no Intel. Thus makes Obito stronger.
Madara is far stronger due to his arsenal of destruction.
Obito due to his kamui renders this kind of arsenals to useless such as PS,Shinsuusenju,TBB.
So all depends on what you mean by stronger.