Personally I would not recommend wearing a poncho when doing the WHW, especially when there is a strong wind blowing during the last few days. I found it quite dangerous at times as there was a real danger of being blown off the hill sides.

What ever you wear there is going to be a condensation problem, so you will be as wet inside as outside. Under those conditions; and if I were doing the WHW again, I would wear my Buffalo Shirt and allow my self to get wet, but I would stay warm because of the material design/action of the shirt.