These speculative conversations can be fun.
First, ask your buddy why this was the war rifle of choice for so many countries...it's not because it tickles.
I'm assuming you are talking about a normal situation, say up to 150 yards and Superman isn't on the other end. In that case you win in my opinion. If it's 500 yards distance and Thor is on the other end, your buddy wins.
This IS a 122-125 grain bullet at a muzzle velocity of about 2,450 fps we're talking about, not a 40 grain .22lr at 1100 fps. It's got, as I recall, about a 15% ballistic advantage over a 55gr. .223 that's currently in use by our armed forces. Does he think they are trying to reach out and goose someone who will then spend ten minutes returning fire?
I'm sure your pal is a great guy. Not the sharpest crayon in the box, on the other hand. Be gentle when you tell him he lost....