Both versions have the same jersey cotton inner layer and the same layer of polyfil. The only difference is the outer layer - microfleece in one and jersey cotton in the other. By nature of the fabric, microfleece is a bit more cozy and puffy, and cotton a bit more breathable and flexible. Both versions should be used in rooms at an appropriate temperature for a baby. We offer both versions to give our customers a choice based on their fabric preference. Please keep in mind that the cotton version will be more likely to shrink with laundering.