Story thought emphasizes subjective human experience, the primacy of individual actors, narrative and social ordering, messiness, edge cases, content, and above all meaning.
System thought emphasizes 3rd-person descriptions of phenomena from a neutral perspective, the interchangeability of actors and details, categorical or logical ordering, measurements, flow, form, and above all coherence.
Example. We’re all systems thinkers about physics; but we’re almost all story thinkers about love, at least at the level of action. We may blend modes, but when we marry, we don’t look at our spouse and think: “Well, you or probably one hundred million others would work.”