The m6a2 has recoil comparable to... probably an MK16 or K2 or SG550... really low, I think it CAN be a 3 hit kill, 4 hit kill usually, good fire rate, good accuracy
The m416 is always a 4 hit kill, sometimes 5. Good fire rate, good accuracy, good recoil, integrated scope
I choose the m416 because any gun with burst capabilities annoys the shit out of me