My opinion is if you're a top 2% shooter, then you MAY have the ability and dedication to turn double cocking into an advantage on SOME stages. Otherwise, stick to single cocking. I've seen very few people develop the ability to turn double cocking into an advantage as it requires that you gallop the pistols; two shots that are very close, but are distinguishable from each other by the human ear. It sounds like a loud cadence of a horse galloping; ba-boom, ba-boom, ba-boom, ba-boom, ba-boom. The problem is you're walking a thin line from double discharging and, because it is a progressive penalty, can over the course of a match lead to a MDQ. It's a gamble.
I'd start with single cocking and if you turn out to be a top 2 percenter, then learn the double cock gallop and let the stage dictate which method you use for that particular stage.