Ideally pairs or individuals allows the most freedom. Time is a never ending problem, there is never enough. Daily rubrics would be helpful for students to self-assess their contributions. Have enough space and time for groups to isolate themselves is important as this is a noisy process. Allowing others to view and comment on the presentation is important to ensure a higher level of quality and to provide a target audience.
Presentation can be to a class, to other classes, or outside groups.
All have some value and are useful depending on the subject and content I'm working on at the moment. Local open access TV or cable Classroom screenings. The makers of the project are often the most critical of their own work once allowed to step back from the production and observe others observing.