All great points above, however, I will also give my thoughts since I've owned 3 legacy MX's each with a diff combination of EAP/FSD/MCU.
'16 P90D has EAP and MCU1.
'16 75D had FSD and originally MCU1 -> paid to upgrade to MCU2
'16 P100D had EAP and MCU2 -> paid to upgrade to FSD
First off...