This study examines how evidence is used differently in argumentative discourse compared to individual arguments. Applying a 1 × 2 crossover study design, 37 secondary school students were asked either to discuss a social issue with their partner before individually writing an essay outlining their opinion or, vice versa, first to discuss and then to write. As background information, they were provided with pieces of evidence with different levels of quality. Dialogs and essays were analyzed regarding (a) the type of evidence and (b) the way evidence was used. Results showed that in their essays students referred more often to the pieces of evidence provided to them (shared evidence). In contrast, they used evidence more often to address the opposing viewpoint in dialogs by incorporating it in a more elaborated (clearer) line of reasoning. Findings suggest that dialogues are a more effective tool than individual writing production, and the study provides first hints regarding how to design curricula that will encourage students to use evidence in a more sophisticated way in their argumentation.