Being a zip allows vent warmth, zipperless jerseys are generally crafted from extra breathable components to stay away from overheating. Most chamois have an interior foam padding wrapped in very low-friction, anti-microbial cloth. The better types have much less and/or smoother seams and much more anatomical cuts to circumvent bunching. https://getidealist.com/story19144666/not-known-details-about-winter-cycling-gear