Is merino wool or synthetic better for a base layer?

Merino wool (as in the Smartwool and Merino.tech picks here) is prized for natural odor resistance and warmth even when damp, while synthetics like Under Armour's ColdGear tend to be cheaper, faster-drying, and more durable. Verified-purchase volume in this pool is strong for both camps; the right choice depends on whether you prioritize multi-day odor control (merino) or wicking speed and price (synthetic).