I should have been more specific (will edit in a sec), the question was aimed at the benefit for the decision makers. NK leadership is going down if they launch

I should have been more specific (will edit in a sec), the question was aimed at the benefit for the decision makers. NK leadership is going down if they launch a nuclear strike, independent of how the counterstrike is done (so their show of strength etc. is of limited importance). But SK/US leadership has to consider nuclear retaliation if they attack NK, in which case it becomes a bad decision in the eyes of their voters, even if they ultimately remove NK leadership. [edit] tl;dr: Having the weapons is an advantage for NK's leaders. Using them is their end.