Well Darth Nox, it is obvious, with his own power he is not ofc more powerfull than Wrath but with powers he gained he is more powerfull than Wrath.Emperor didn't choosed Wrath because he was most powerfull but because of other things, he needed someone he can manipulate, I doubt you could manipulate Dart Nox like that.I am speaking about them as male it's easier for me.