Merino wool is an excellent choice if you're skiing multiple days in a row or hate that funky smell gear can develop. It's naturally antimicrobial, so it resists odor far better than synthetic options—even after long days on the mountain. It also feels incredibly soft against your skin and does a great job regulating temperature, keeping you warm without overheating.
The trade-off is price and wet performance. Merino balaclavas cost more than polyester fleece, and if the fabric gets soaked—say from heavy snow or sweat—it can lose some insulation and shape. It also only offers moderate wind resistance compared to windstopper or softshell fabrics.
Go with merino if you're doing multi-day trips, have sensitive skin, or prefer natural fibers. For single-day resort laps in wet or extremely windy conditions, a synthetic or hybrid option might serve you better.