In my experience it seems that chill touch seems to average consistently higher damage. Ghoulish numbing seems to have more variance. I think that it might have a higher top end and a lower low end than chill touch when both are perfected. My questions are these:

Are my observations correct and that's how the damage shakes out?

When you choose one or the other in combat or in pk do you choose them based on the type of opponent, or based on which side effect you hope to have hit?

Thanks for the advice.