I've been a long timer reader, but first time poster. I could probably write a dissertation on softshells, WP/B, EPIC, etc., but I can't choose between a nylon or polyester face for NON-WP/B, i.e. Windshirts, softshells, etc.
In the past, I remember seeing many Pile/Pertex systems (Buffalo, Montane, etc.) mimicked in the U.S. with similar principles, i.e. Marmot DriClime: a wicking interior with a tough, nylon face. The often polyester-based interior would wick away sweat, and the nylon would absorb it, spread it out, and through a large surface area let it evaporate quickly.
Lately, at least in the U.S., I've seen many jackets and shirts that have always been nylon switch to polyester, like this years Marmot DriClime. Cloudveil's Enclosure jacket–well known for a great belay jacket–changed from primaloft/nylon to primaloft/polyester.
So why are manufacturers moving to Polyester?
Correct me if I'm wrong:
With nylon being hydrophilic, water/vapor will come up through the interior polyester, and will be absorbed by the nylon. The nylon will spread out the water over its surface so the outside air can take it away.
With polyester, the water will be pushed by heat/pressure/diffusion through the polyester to the surface. The surface polyester won't spread the water out, and polyester will not absorb the water (as quickly as nylon, at least)
So, it seems to me that nylon is the better material for a jacket face: once the moisture starts reaching the face of the jacket, the heat you create is pushing it out less. The best way to get rid of it is have outside air move it away. In this sense, surface area is king, and nylon will allow the moisture to spread and be take away faster.
But again, the polyester will absorb less outside water. I'm not sure if the polyester not absorbing the sweat moisture also increases the ability of the sweat to get outside the jacket.
I do know one thing: most extreme mountaineers, hikers and the like still stick to a nylon face. Is it just because of the extra durability? Is polyester–aside from being a bit less tough–actually superior? I think there's more to the analysis than a toughness factor. Maybe someone could explain?
