I layer, but like cover-alls better than bibs. I've found that both are too warm for walking long distances. I put them in my pack until I'm on the stand. But if it's cold out I'll put them on as soon as I'm going into the woods and just walk slower or unzip if I get warm, or take off your hat. On the really cold days is when I've noticed the biggest difference. The jacket and bibs let cold more cold air in during periods of wind. But, that is just my opinion!
Good luck.