m2m slot

Which Slot should i use or does it matter? I'm looking at the M2M_32G (top) or the M2P_32G (bottom). slot stasiun play The top slot has a real good heatsink on it and i don't believe it will fit the bottom I've only got 3 regular SSDs so the sata 3 4 and 3 5 on the top slot are unoccupied