what are the advantages of a cohesive group?

Answer 1

From Wikipedia:

The bonding together of members of an organization/unit in such a way as to sustain their will and commitment to each other, their unit, and the mission

Good luck....

Answer 2

A cohesive group will usually work together toward a common goal and for the common good. There is usually little friction or disagreement in cohesive groups, and the members are usually satisfied with the group. However, on the negative side, I don't think there is as much creativity in cohesive groups.