The following is a brief excerpt from a book I often reference:
“Little wonder that the church historically has usually grown the fastest and evangelism has proved the most effective, in small, informal fellowships. These may be fledgling “church plants,” or small groups withing larger more established congregations.14 Even the exceptions to this trend, as with mass response to large crusades, tend not to bear lasting fruit unless newly converted individuals are linked up with local congregations for ongoing nurture and discipleship.15″
His sources are:
14. Gibbs, Eddie. I Believe in Church Growth. (Pasadena, CA: Fuller Seminary Press, 2000), 234-274
15. Catherwood, Christopher. Five Evangelical Leaders. (Wheaton: Harold Shaw, 1985), 201-202
~ One thought is that this must be based on data from the Church in the West. So is it applicable to the Church in the East?
~ Another thought is that if its “small groups withing larger more established congregations” then you could probably say that both large and small informal fellowships are good for growth.