An auditorium is a place of learning. You might want to start by checking the degree of soundproofing. You could then check the availability of equipment - is there a blackboard or flipchart, for example, or a video projector? Auditoria for 50 people or more will need sound amplification equipment.
The best exhibition spaces have plenty of room to help people circulate. For example, a café filled with small tables wouldn't be considered an exhibition space in the traditional understanding of the term!