the way it is structured, and a bunch of other factors.
Underneath all of those factors is the need to send young adults out knowing how to work cooperatively with others.
Many gifted students don't like group work, because they think and work and produce so much faster; others slow them down. It's even more important for them to learn to work well with others. That's a life-skill that's essential for all of us. It's important to structure group work so that the gifted don't have the burden of "carrying" the group, but just their own portion of the pie.
Some students just learn better with a group, and others better on their own. Since we don't have the resources to completely customize every assignment for every student, both have to be present to provide balance, so that all are sometimes challenged with working outside their comfort zone, and sometimes working within that zone.
Group work is an important part of the larger picture. It's good for getting students to dive into something challenging in the beginning, because they are more engaged if they aren't intimidated, and the support of a group is important. It's good because one of the important ways the brain processes new information to understand it and move it into long term memory is to talk about it with others. It can also be time-efficient. In the era of constant testing and test-prep and demands to prove that we spend every day teaching to the test, longer-term projects are few and far between. A group can produce a research project much more quickly, because each member is only doing one part of that assignment, yet they are all engaged in the process of gathering, analyzing, organizing, and reporting information.
All of that said, independent work is also important. In the end, students need to be able to demonstrate that they've learned something without the support of a group. That's the usual sequence in my classroom: group work early, independent work towards the end of a unit.