Both wool and synthetics work, but over the years I have mostly switched to synthetics. I still use the 20 year old polypro jacket that has kept me warm while in violent storms, 120 feet under Lake Superior in a drysuit, and comfortable on first dates. The elbows are now wearing out, but it is still good for rough jobs. I would be wary of swathing myself in most synthetics while flying, although I would prefer Nomex, which will protect far better than wool. IME, the biggest drawback to wool was the increased weight when wet (although still warm) and the fact that moths eat holes in it. I have not had a problem with campfire sparks and synthetics, probably because I mostly use stoves these days. I also appreciate the easy care afforded by syns. While material is important, it is important to pay attention to clothing construction details - ventilation features are extremely important for improving the versatility of any clothing.