Touring, relaxed centuries, mountain bikeing, fun easy riding = triple

hard training, fitness riding, racing = double.

If you race on a triple you will be dropped. In a race in your 39x23 you may be more tired then some one who spins a 32x27 to the top of the mountain but you will be there first and thats what wins the race.

fwiw thats the way I look at the double/triple argument