The fundamental difference between the thinking of Nines and that of Fives is that Nines are impressionistic, involved with generalities, imaginative ruminations, and fanciful situations. Nines typically do not concern themselves with details, nor are they usually good at following up once they have acted. By contrast, the thinking of Fives is highly focused, penetrating, and almost microscopic in the narrowness of its frame of reference. Fives love details, losing themselves in research, scholarship, and complex intellectual pursuits. They think in depth, concentrating so much that they block out other perceptions (eventually to their detriment). By contrast, even brilliant Nines tend to have problems concentrating; they also tend to lose interest quickly and to allow their attention to drift off when they become bored or anxious.
Nines tend to spin grand, sweeping, idealistic solutions to problems, while Fives tend to speculate on problems, then on the problems that their problems have raised, then on those problems, ad infinitum.