I don't have enough experience to tell you which side is higher than the other, though the fact that we do not live in some kind of absolute hellhole suggests that the curve is tipped toward the right (benevolence). Yet I do get the impression that it's one extreme or another.
The sociopaths do tend to burn themselves out eventually though. There seems to be some kind of what's effectively karma, which probably comes from peoples' lies eventually catching up with them. It's overall better to be benevolent.