There are good and bad for both lectures and small group work as seen before, but you can't have one without the other. A lecture is an easy and effective way to pass on a lot of information at one time. It is often well structured and that makes it easy for the student to find information while studying.
That being said, it is very difficult to pay attention in a lecture situation for very long. Students zone in and out. They end up only writing the information down and not processing it in a way they understand. That is where small groups come in. It may take up more time, but the students help each other in their learning process. When one student teaches another, the information in more achored in his or her memory than before.
In order for the students to learn and retain information, they need a lecture to get the information and small groups to process it.