Base layers made with synthetic materials like polyester are very durable, stretchy, and quick-drying. They have good moisture-wicking properties and dry quickly, keeping you dry and warm. These base layers are excellent for intense activities.
Base layers with wool have good temperature-regulating properties, meaning they keep you warm when it's cold and cool you down when it's warm. A set of base layers with wool is ideal for activities with varying intensity, such as downhill skiing, where you alternate between intense runs and sitting still on the lift. Merino wool is often used in base layers because it is softer against the skin and doesn't itch like regular wool.
Base layers made of a blend of wool and synthetic materials give you the best of both worlds! Synthetic materials tend to start smelling after a while. Here, wool's antibacterial properties improve the performance of the blended material. Wool can be sensitive to wear, but polyester makes the base layer more durable and easier to care for when washing.