When selecting base layers for the mountains, the choice often narrows to two exceptional materials: Patagonia’s Capilene (synthetic) and Icebreaker’s Merino wool. Your decision ultimately hinges on prioritizing ultimate performance versus versatile comfort.

For high-output aerobic activities like trail running or ski touring, Capilene delivers superior performance. Its engineered polyester fibers excel at moving sweat away from your skin through capillary action, a process known as wicking. This rapid moisture transport keeps you drier and cooler during intense exertion, minimizing the risk of a dangerous chill when you reduce your pace. Synthetic fabric is also exceptionally durable and outlasts natural fibers over thousands of washes, making it a long-term investment.

In contrast, Icebreaker’s Merino wool offers a uniquely comfortable and luxurious experience. It is naturally odor-resistant, allowing for multiple wears without washing, and provides reliable warmth even when damp. Its soft, non-technical appearance makes it perfectly suited for wear at a café or around town without looking out of place. A critical, often overlooked advantage is wool’s inherent fire resistance, a key reason it is specified by emergency service personnel who may face flashover risks.

In summary, synthetics like Capilene are the undisputed champions of high-intensity movement, prioritizing efficient moisture management and durability. Merino wool, however, is the versatile all-rounder, offering exceptional comfort, odor control, and a blend of safety and style that transitions seamlessly from the trail to daily life. Your specific activity should guide your choice.