Wool outer wear requires less overall bulk than the synthetics do, {talking about maintaining core body temps}, especially if you are not using "any" type of water/wind barrier, which depreciates the breathability factor too much for me. With wool I just adjust my long johns for the conditions. With synthetics I have to layer up quite a bit more than when I have all wool on.
Sleeping Indian Wool "Shirt," Wool Pant, and a Wool hat, proper longjohns for conditions, presto, good from +75F to -20F, if the wind is howling and I'm Sitting, I'll put on the Wool vest with the wind liner, haven't needed it yet.