I think both are equally important. Drama CDs aren't like games—they have spoken lines and internal monologues that give you a deeper understanding of the plot and what the characters are thinking. But at the end of the day, a drama CD is all about the voice actors' performances. So their voice and acting ability really matter a lot
I listen to drama CDs primarily for the voice actors.
Of course, the story is important too, but since drama CDs are an audio-only medium, I believe the voice actors are the most crucial element in immersing oneself in the narrative.
Depends actually......if it's the trope of story that I'm not interested in, I'll skip most of the time. But....BUT......only for that one favourite, which is UMEHARA Yuichiro, I'll listen some samples first and so far the stories of his dramas are doing fine (at least for the ones I've heard)