Is synthetic or merino better for backcountry skiing?

For the uphill approach, synthetic is generally better because you'll sweat heavily and need the fastest possible moisture transport and drying. For the descent and camp, merino's odor resistance and warm-when-wet properties are advantageous. Many experienced backcountry skiers use a hybrid approach: synthetic base layer for the skin up, then switch to a merino top for the descent and evening. If you can only choose one, synthetic's superior moisture management during the high-output climb makes it the safer choice for backcountry use.