Another dimension of comparison: the ways in which I intuit (rightly or wrongly) each activity to be healthy or unhealthy for my personal development.
With Twitter, there is this great Unease (in which many of us share) that the actual activity of Twitter is both addictive and destructive of one's inner life, regardless of who you interact with. On the other hand, I have also found my thinking challenged and broadened by reading and interacting with people I'd ordinarily never hear from.
With church, it's sort of the opposite; I understand the activity of weekly communal worship and eating itself to be fundamentally (profoundly) sound; but that there are also Problems caused by tribalism among the particular people you might find yourself with.