The whole confusion seems to be a lack of information in the arguments as to what exactly they are brainstorming about. Is it a new movie/book idea or solving a programming problem, creating a software architecture, planning an invasion or just discussing how to improve a process etc... All of these are different situations and in some cases, brainstorming might work better, others are best left to individuals. You could try and guess which is good for which as a practice and you will still probably have some subjective cases where one might be better than the other. So, lets not make generalized statements please.