Tobi is not Obito because:
1. I don't understand what would motivate him to do the Eye of the Moon plan.
2. Tobi is a manipulater and at points a liar. Seriously hard(for me) to imagine someone who cherished friendship and teamwork to become some grand scheming big bad.
3. Assuming that Tobi was the one who helped Itachi kill off the Uchiha's and not Madara, why would Obito do that? Obito was kind hearted.
4. The time between when Obito died and when Konoha was attacked is just too small for Obito to have the Jutsu he had. Minato himself even said his S/T ability was greater than his own and Tobirama's. He even said that Madara was the only one who could have pulled off the Konoha attack. How can Obito go from Genin to Madara level in that short of time?
Now in my opinion, it is reasonable to believe that Obito's body is being used as say, a vessel for something else.
