Are all small groups equally beneficial?

The answer to the question in the title of this post depends on how you define the goal of small groups. Small groups can be a tool to draw people into a sense of belonging rather than consuming. This can be easily identified by how they refer to the church. Do they call it YOUR church or OUR church?
Small groups can be a tool to of spiritual formation or discipleship. Ideas are shared, tough questions are asked, and truth replaces the lies we believe as individuals are conformed to the image of Christ.
Small groups can be a tool for social change. The cumulative result of shared effort is greater than the sum of individual contributions. Fatigue and simple routine can easily manifest when a person challenges an issue alone, but mutual encouragement and creativity flourish when there is a shared responsibility for results.
Small groups can be a tool for behavior modification, as evidenced in thousands of self-help and 12 step groups around the globe.

This study provides 4 descriptions of the effectiveness of groups that caught my attention.
1. "Members of small groups...are more likely to attend worship, tithe and volunteer"
2. "Any type of small group will benefit your church...because of the belonging and commitment they foster"
3. "Frequency of attendance is more important for successful small groups than is length of attendance."
4. "The best way to get people into small groups is by personal invitation"

Does your experience coincide with these findings? As you reflect on your past have you found participation, belonging, frequency, and personal invitation to positively influence your obedience to and sense of intimacy with Christ?