synthetics generally are better. I'm not a big under armour fan. A pair of sugoi midzero tights should do the trick. I'm actually psyched to try out cwx stabilyx insulated tights, but probably overkill. The key is to move moisture away from the body and not have it cooled by the wind. So up top a thin shell over a skin tight base layer and maybe a half zip mid layer depending how how hot you get.

This works great for running. Should work well for biking, but I haven't gone through a winter yet.