Obito admitted inferiority to him. I think it's really wrong to say that Obito threw out thr fight just to make Kakashi break his seal: Obito tried to kill Kakashi multiple times and he also even tried to bertray the Alliance and take his side. If Obito did something like Itachi with Hebi Sasuke, it would have been made clear... he wouldn't have admitted inferiority to Kakashi as he did (
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), he'd rather would have mocked him for having helped his plan, I think that's logical. I simply think that Obito decided to fight Kakashi one on one to settle everything with him; once he saw that he wouldn't have won, he decided to take advantage of what would have been his loss anyway, putting his life completely on the line. I think that War Arc Kakashi is portrayed as slightly stronger and better than Obito: while Obito has more raw power, Kakashi has more skill and he is the better ninja. And Obito is one of the strongest people in the manga.