Hey, I'm with him as far as ridiculousness. And it shouldn't be just in Naruto's head, it should be both their consciousnesses entangled. Assuming that the Kyuubi can no longer bend Naruto's mind to his will using "hate" to cloud Naruto's mind, I would still say that the 9-tails has an advantage over Naruto mentally.

We, of course, are not assuming that Naruto is taking on the Kyuubi physically, instead, we are assuming that Naruto's mental prowess is going to trump the Kyuubi's. Given the 9-tails age and power, I would say the 9-tails has the edge, mentally.

The only way I see Naruto winning this battle is simply pure stubborness and an unwillingness to bend to the left or to the right, no matter what reasoning or logic you throw at him. Basically, Naruto would rather kill them both (suicide) than have the 9-tails win. Kyuubi is smart enough to know that Naruto is determined (or stupid) enough to do it, so he will probably accept defeat. That's the only way I see Naruto winning a mental battle here.