CuNiFe is a lot weaker than AlNiCo 5. It's closer to, but still weaker than, AlNiCo 3. As far as the magnetic circuit goes, it's still pretty much the same as a PAF, due to the fact that the pole pieces are in almost the same places. The other differences, a lack of bar magnet, low permeability, don't really matter, aside from how the different materials influence the Q factor. By and large, a Wide Range Humbucker is a PAF rip off. It's not fundamentally different.