Often the down wind leg is not DDW, but maybe 210-220. Not quite enough for broad reach. You can pole the genny way out to windward, or bring the boom to windward w/genny to leeward. (Yes we all know about the safety issues). In theory, which is faster???
It isn't usually a question of which is faster in terms of raw boatspeed. More often, the question is, how can you get to the next mark the quickest?
If the mark is very close to dead downwind, I set the sails wing and wing and, as the wind direction moves a few degrees one way or the other, I try to keep heading for the mark. If the wind direction shifts so far that I can no longer do so without gybing, then I like to gybe both the main and jib, and sail "wung out" on the opposite tack. Eventually the wind gradually shifts back a few degrees the other way, in which case I might have to gybe both sails back to the other side. The point is to generally sail as close as you can to a straight line to the downwind mark, because that's the shortest distance. If you decide to broad reach, then you have to gain enough speed to compensate for the added distance that you'll have to travel in order to get there. Cruising boats can't always do that.
It might seem obvious, but in order to get to the downwind mark fast, you have to get downwind
as fast as possible. But the mark isn't always dead downwind. Sometimes it's off to one side of dead downwind. When that happens, you can usually get there the fastest (with white sails) by sailing wing and wing, approximately dead downwind, even though you're heading to one side of the mark. Then, when you get far enough downwind, sail the rest of the way to the mark on a beam reach. By sailing the last short distance on a beam reach, you'll approach the mark very fast while the others are approaching it very slowly, and you can literally coast around one or two of them, and still start the next leg of the course with good speed. If the windspeed is fairly steady, that strategy works well. If the windspeed is fluctuating a lot, then I steer dead downwind in the puffs and head up a few degrees in the direction of the mark in the lulls. If the wind also changes direction, as it often does in a lull, then I might have to gybe the main or jib and start reaching.
This downwind strategy isn't as applicable to the lightweight, fast racing boats, because they can accelerate to speed on a broad reach much better than a cruiser or racer-cruiser. Also, some boats with cruising chutes can broad reach much faster.