Work groups tend to compete inwardly, with members competing against each other for favor, recognition, etc. High performing teams compete, but with those outside the organization.
Work groups tend to be task-oriented and characterized by members who follow their own personal agendas. High-performing teams are goal-oriented. Members work towards the achievement of the team goals and agenda, rather than pulling in different directions.
Work groups tend to be autocratic and hierarchical in nature. Teams, on the other hand, tend to be participative and self-steering within the goals of the team.
Work groups tend to tolerate each other, while teams tend to enjoy each other. Differences in teams are welcome and encouraged, while in work groups, differences and disagreements are suppressed.
Work groups tend to avoid risk and maintain the status quo. High performing teams tend to accept risk.