The small group dynamic works just the way Jesus intended. Mega churches realized a long time ago that they must rely on these small groups to multiply God's kingdom. Some smaller churches tend to to ignore this.
The small group is really nothing more than the same concept of a "sunday school class" ... it's just that the mega's have such huge numbers that can offer a variety of "subjects".
We visited a mega a few times in San Antonio - I did not care for it at all ... always felt like an Amway convention to me. That and the Sunday morning class we were visiting was right across from the teenagers - we could hardly hear ourselves think due to the extremely loud music ...
So now - we're at a tiny church - no need for small groups .. we ARE a small group... laugh...
I say that understanding it is all based on personal preference - however I must say that there seems to be a lack of depth in majority of folks I know that attend extremely large churchs.