Pretty much as 50 shooter said.
Also several other factors between SFP & FFP.
First is cost.
FFP is generally more expensive than SFP.
Second, with the reticle staying the same size, but target getting larger/smller on SFP, if you do your due diligence, you can zoom out for greater drop.
IE. IF your MOA/MIL matches at say 10 power, theoretically at 5 power, each MOA/MIL is now doubled. Again, due diligence is involved in actually verifying this at the range.
It may not be the perfect 10 power or 5 power.
Third, have you seen how small a FFP MOA/MIL reticle is on low power?
Not particularly conductive at low light levels in a hunting situation.