Well if you think about it so far Bee and Naruto haven't even managed to harm the Jubi with the full scale assaults they've made and that was before it's transformed, if you think about it even if the 9 tails is fully powered there is no possible way it would be stronger than the ten tails even in its weakened state and before I believe I read something about the Jubi starting to regain strength so if you think about it like this 9 tails=2+3+4+5+6+7 and as we are aware, at this moment the Jubi=1+2+3+4+5+6+7+Small portion of 8+Medium portion of 9+Own power, so if you see it like that then There is no possible way that Kurama is stronger than Jubi.