The Case For Group Study
Teaching someone else is one of the most effective ways to consolidate your own understanding. We quiz each other, challenge each other's explanations, and occasionally disagree.
The Case Against
Most "group study sessions" spend the first 25 minutes catching up. If you're not disciplined, group study is just socialising with guilt.
My Conclusion
Group study works, with structure. Agree on what you're covering before you meet. Take turns teaching topics. Set a time limit and stick to it.