Just wondering why you think Cit is more unified than SF but not as much as C&G? If you mean unity between the member alliances, from a layman's point of view the only real way to gauge a bloc's unity would be going on history and their presence on the forums, but imo it seems pretty hard to say who is more unified without actually having been part of the others. Every bloc is going to have small disagreements here and there at times, but I don't think any of the four (Cit, SF, C&G, FB) have had severe conflicting ideologies that have created lasting tension internally.
The only other option I suppose would be treaties, in which case yeah, not all of SF is friends with the same people. I don't know enough about the other blocs to compare, and that may prove true to your original statement.
On topic though: Like others have said, the real superpowers to me are the blocs atm. The way that the treaty web has been the past 2+ years, there's never going to be an individual alliance holding immense power over others; it comes down to how well connected said alliance is.