You'll get a lot of different opinions, depending on where people go outdoors, what they do there, and for how long. The differences of opinion are valid.<br><br>Me, I've been wet a lot, one way or another, and I really value synthetics. IMHO, anyone who's backpacked through 5 straight days of rain is going to learn to value synthetics, especially fleece- nothing natural EVER gets dry. Some people like wool, but it's less comfortable (for me, at least) and MUCH heavier. It retains insulation value when wet, but is even heavier when wet, and much slower to dry. <br><br>Cotton kills. Not worth discussing outside of the tropics. I won't even pack cotton t-shirts or underwear. I wouldn't be a bit surprised if blue jeans kill more people in the wild than bears do.<br><br>I probably wouldn't have replied, but you mentioned Windstopper (synthetic fleece bonded to a layer of expanded PTFE or similar). It works as advertised, it's sort of nice in the high country where the wind never stops, and it's quite the fad right now... but I don't think it's worth the money. A combination of a simple fleece jacket and a light shell works as well or better in the wind, insulates better in cold (the fleece used in Windstopper tends to be very thin), is MUCH more versatile (you can wear either one alone), and costs a great deal less. I've also seen Windstopper retain moisture on the inside in cold weather, which simple fleece does not do. Not good.<br><br>I'd save the money and put it into rain gear, where even the best is mediocre.