If you have the opportunity to choose collaborators, consider this:
The whole truly can be larger than the sum of its parts. Through collaboration, we can produce documents that we alone could not imagine. Collaborators can inspire us, keep us on task, and help us overcome blind spots.
At the same time, collaborators can become obstacles, requiring constant supervision. In group situations, other students can fail to attend classes or out-of-class meetings; they can ignore your efforts and just focus on their own missions or visions about ways documents should be written. When collaborators don't do their job, they can become an annoyance--just another obstacle rather than a support and an inspiration to colleagues.