SakashiroI put reactive armor on my Mamba, with grade 5 thermal and layered plating, because that gives it a balanced 16/16/17 percent resistance against kinetic, thermal, and explosive damage. On the other hand, I have no HRPs, only MRPs. The reasoning behind it was this: I need at least some hull boost to deal with phasing sequence weapons that bypass shields, and I need increased module integrity to deal with reverb cascade weapons that damage the shield generator even while shields are up.
During the bounty hunting CG the MRPs never came to use. Reverb torps are rare, even in PvP. So I might be better off by replacing the MRPs with SCBs. The reactive armor however I will keep, because phasing weapons aren't rare at all, even some NPCs use them. Besides, unlike HRPs, armor has its own module slot and doesn't occupy any of the optional ones.
On medium and small shields reactive or military makes sense. Although the former is more reasonable for for PvP build while latter is usual choice for PvE. And yes, Mamba and FDL are better with SCB than HRP especially in PvE builds because NPCs do not cencel banking.