Many people would say so, but I’m not so sure. I think that Naruto and Kurama did so well against the other Bijuu when they were being controlled by Obito because perfect Jinchuriki can use chakra much more efficiently than the Tailed Beasts, especially when the Tailed Beasts are being forced to fight against their will. Kurama did claim that he’s the strongest because he has 9 tails, but Gyuki said that was wrong. It makes more sense to me that Kurama was just boasting, as opposed to Gyuki just lying about the number of tails not mattering. Gyuki it would be out of character for Gyuki to lie about that, and going by the “tails = power” logic, Gyuki would be very high up in the hierarchy, only behind Kurama, so he wouldn’t really have much reason to want to deny that having more tails makes you more powerful