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.
Dance is about movement. The venue for this kind of event should be spacious enough that everybody participating can feel free and not have to worry about bumping into one another. You might want to check whether it includes a changing room, shower, and toilet.