My base layers of long underwear and socks are almost always merino wool, along with various merino wool caps, neck gaiters, and sometimes liner gloves. I actually wear merino wool socks every day, all year long.
Most of the rest of my hunting clothing is synthetic, and that is because it is light, compactable, and warm when needed. I like down, but have gravitated now to PrimaLoft or some other similar fill insulation to stay warm if the insulation gets wet. Kuiu has recently come out with down jackets where the down is DWR (durable water repellant) treated to minimize water absorption and drying time. I will wait for some of the real world reviews before I venture out with the new Kuiu down clothing. I like the soft shell materials from Kuiu, Sitka and others. I've worn that gear in the Yukon Territory and the Rockies, and it works well, as long as I make sure to stuff PrimaLoft mid-layer jacket, vest and/or pants into my pack. Lots of trips involve travel by air with all my gear, including sleeping bag and pad, bows, arrows, optics, clothing, etc. I don't have the room for excess bulk or the weight allowance for excess mass in my gear, so the lightest, most compactable gear is what I look for. In most instances, wool is not the best option for me to use for my middle or outer layers, although a second pair of merino long underwear, a non-bulky merino sweater and/or a Pendleton shirt can be a good option. Of course, I also have good hard-shell rain gear, with my favorites being Core4Element Torrent (quieter) and Kuiu Chugach (drier), that can keep out wind, rain and snow.
HOWEVER -- I do have quite a bit of wool other than socks, long underwear, caps, gloves, and other next-to-skin items. I also have whipcord wool pants that are fairly light and tightly woven, Pendleton shirts, merino wool (and other less desirable wool) sweaters and LaClair Longhunter wool pullover and hood/cape. I gave away several pairs of heavy wool pants because they were far too bulky and heavy for me, so I never wore them. So, except for the heavy wool pants, I am adequately prepared for hunting completely in wool too, which I am sometimes known to do.
I also have a ton of fleece, which I think is the greatest stuff ever for silence and wears like iron. It also comes in lots of my favorite patterns. Fleece isn't the warmest, lightest or least bulky material on the market, but it works very well in most hunting conditions, even when it is not the best option available.
Cotton is good for some conditions, but in winter it can kill you, and when wet it is abrasive. I only wear cotton in mild, dry weather and never in my boots where it is a leading cause of blisters.
Allan