If we are talking about shedding, Rex rabbits only have the under fur layer to shed unlike rabbits with the longer layer that also gets shed, so the amount per size is less. Not sure about the cold part, but those with the longer fur have added protection from the cold also. Just like backpacking, layers equal more insulation because of dead air space so regular furred rabbits have it between the longer and underfur layer and rex rabbits only have the one layer so it does have less R value. At least that's what I think but I went thru 12 books and really couldn't find anything on a Rex as far as cold weather versus the regular.