In Ephesians (4:16) Paul talks about the effectual working in the measure of every part. This often does not happen in a big group. In a small group everyone gets the opportunity to play their part in building up the Body of Christ.
For the body is not one member, but many. If the foot shall say, Because I am not the hand, I am not of the body; is it therefore not of the body? And if the ear shall say, Because I am not the eye, I am not of the body; is it therefore not of the body? If the whole body were an eye, where were the hearing? If the whole were hearing, where were the smelling? But now hath God set the members every one of them in the body, as it hath pleased him.
Romans 12: 4-8
For as we have many members in one body, and all members have not the same office: So we, being many, are one body in Christ, and every one members one of another. Having then gifts differing according to the grace that is given to us, whether prophecy, let us prophesy according to the proportion of faith; Or ministry, let us wait on our ministering: or he that teacheth, on teaching; Or he that exhorteth, on exhortation: he that giveth, let him do it with simplicity; he that ruleth, with diligence; he that sheweth mercy, with cheerfulness.