There is zero difference in the two. I just bought a guardian FSD V1 and it was weaker than the one I engineered with farseer so I went out there and added the experimental effect "mass manager" now I have two identical FSD's zero differences between them!
Wrong. There is a difference FSD V1 mass manager has a longer range than FSD G5 range+mass manager in all cases. They are not identical, check the optimal mass, 1693T vs 1856T, will add several LY jump range to any ship. The only way they could be the same is if you broke the engineering on the V1 FSD by redoing the increased range, removing the extra benefit.