They are inextricably bound together. Each enriches the other, and motive is the key to both. What do people want, and what lies in their way? What are they prepared to pay to get it? Why is it so important? What is the inner conflict?
What is the backstory? That doesn’t mean justification, but it does mean understanding…it means fleshing them out with wounds to the mind and heart, hungers, fears, etc. And what is the most fun of all, relationships.
And the big one—the arc I’d develop. No change, no journey, equals no story. Let us explore the things which change people, step by step, from where they were in the beginning to what they become. This can be the most difficult and the most rewarding of the whole work. It is the essence of story. People read because they care about the characters and what happens to them. They will read half the night to find out!