although i like hiruzen better id have to say danzo has the clear advantange because of all his sharigans. see he can just act like one of those two killed him like oonoki kills him with dust release but then he can use izanagi and wait until hiruzen and oonoki fight eachother and make eachother weak. all he has to do is hide and wait till the rght moment and even if he comes out too early he can just use izanagi again and again. also he has shishuis eye so he can use the ultimate genjutsu on either oonoki or hiruzen when they are fighting eachother and force them to attack eachother. I know its not as simple as this and it will be a long and hard fight im just pointing out tht danzo has the advantage and probably will win