The Dually Series has four LEDs. The "Flood" style lights produce a wide, fairly standard flood beam pattern. The "Spot" style lights have a very narrow spot beam.
The D2 Series has six LEDs. The "Driving" style lights have a long range beam that's fairly narrow, but still has more width than the Dually Spots. The "Wide" style lights have a wider beam with less range than the Driving lights, but more overall range than the Dually's Flood pattern.
You can check out examples of the beam patterns in the individual light listings.