Personally I like the three dot arrangement best, but any tritium sight is worth its weight in gold if you have to shoot in low/no light settings.
I haven't tried the two dot arrangement, but have used the bar/dot system Novak has. The front sight is the standard dot, but the rear has a thin horizontal element. All you have to do is set the ball on top of the bar. This seems to be very fast although not quite as precise as the three dot arrangement.
Early on it was suggested that a single tritium insert on the front sight was workable. That wasn't the case at all for anything except the closest shots.
I haven't tried the two dot arrangement, but have used the bar/dot system Novak has. The front sight is the standard dot, but the rear has a thin horizontal element. All you have to do is set the ball on top of the bar. This seems to be very fast although not quite as precise as the three dot arrangement.
Early on it was suggested that a single tritium insert on the front sight was workable. That wasn't the case at all for anything except the closest shots.