the only reason why obito was ably to control the juubi was because the juubi in incomplete. Right know juubi is just a creature who has no sense of anything, he is just power. If juubi was complete I think he would have fought obito he 9 tails did to naruto when tried to control his powers. So controlling the power was easy for obito then to have to fight the juubi. 9 tails and 8 tails are very powerful compared to other tailed beast so a big part of juubi is missing so controlling his power is not as difficult. pretty obvious but some were flipping out that obito control the 'Juubi' so he is the same as so6p.