Each one of us have different preferences in how to study. Some may choose to study alone, while others prefer to engage into group study. There are number of differences as to compare these two ways of studying. As for myself, I appreciate both depending on what to study.
When studying in a group, many ideas can be gathered. It is widely said that two heads are better than one. Other opinions and comments about a topic can be heard while when studying alone, you will see the idea on the same aspect, the way you view it. In a group study, motivation can also be gathered from your co-students. Because you are on the same track of the lesson, you can get motivated by how others move on with their studies. Friends and colleagues can also be gained when joining a group study. Even if the topic is boring, you can stay alive with fun and bond from others in the group.
On the other hand, studying alone is good when preparing for an examination. When alone, there is silence - which you probably cannot get when studying in a group. It will be a lot faster when having a quiet time alone like when memorizing or reading because there is no disturbance.