Bib tights cost more, but they are worth it IMO for C/A because they stay up better and don't sag so much in the crotch. They also will keep your torso a bit warmer ( which is important, because the warmer your essential organs are, the more blood your body will allow to get to your extremities ). Leg warmers I find not very useful - it's usually cold enough for tights or just wear normal shorts.
They are sometimes hard to find, but skinsuits are actually excellent base layers in cold weather. A plus size person may balk at a skinsuit normally because of the flab it can show off, but in the winter it's all underneath. The usually thin material wicks moisture well. Long sleeve versions are great but are usually harder to find. They are becoming more popular recently for cyclocross and cold weather road racing. Now is a good time to look for used ones on ebay, because many people get new team clothing at this time. Bidding competition for the large sizes can be a bit fierce though.