I haven't made any arrows for a year or two, but about 3 winters ago I had a lot of time and various turkey feathers and made quite a few different styles and combos. The few times I've shot the two fletch I've had mixed results. The better ones were fast and accurate, the lesser ones acted like a well thrown knuckle ball but still tended to find the target. Based on this very limited testing I would have to conclude that maybe the two fletch are not as forgiving of poor craftsmanship'
I've also noticed that nearly all the arrows (which are very long and probably very heavy) used by the Amazonia tribes are two fletch, and usually a longer feather.