I've never been a part of the goin't'hell group, but in my fairly extensive experience as a young adult in an evangelical religious group, I certainly got the impression that the high touch personal approach was taken as more effective. Most people don't really like doing the door-to-door salesperson routine[0]. But they do it because it seems to work - assuming anyone actually answers the door (which is the real rarity). Or at least is effective enough; conversion rates are, shall we say, low. It doesn't need to be high, though, since the risk and reward is so high (failure means more lost, success is a life).
[0] For introverts it can be extremely stressful - practice is the only thing that seems to make the terror go away for them. If the person at the door preachin' the word looks awkward and is stammering, be kind - they're more afraid of you than you are of them :)
EDIT: slight grammar/clarification. EDIT EDIT: This is off-topic enough I'm going to just truncate part of my comment to gist: https://gist.github.com/anonymous/dead25324e4f74ccc183