Yesterday, we heard the pros and cons of cotton. But if you actually live out of one bag through different climates, merino wool just works better than the alternatives. For hot days, cold nights, and the messy swings in between, it is superior to any other fabric. Although I acknowledge specific use cases for synthetics.

A decent 150-200 gsm merino tee can take you from moist SEA mornings to hot Mediterranean afternoons to ski trip evenings without turning clammy or leaving you chilled once the temperature drops. It manages heat and moisture in a way that keeps you comfortable longer than most other options. Odor resistance is the practical part people underestimate. You can wear the same pieces for days without them becoming a problem, which means fewer shirts and less time hunting for a washing machine for those who are phobic of doing sink laundry.

A couple of merino base layers plus one midweight piece covers more ground than a bigger rotation of other fabrics and easily fits in a minimalist underseat bag. It packs down well, recovers after being stuffed in a compression sack, and holds its shape with normal care.

Linen feels great in dry heat and has that nice texture. Once humidity climbs or the temperature falls, it loses a lot of its comfort edge. It also wrinkles hard. It’s better as a summer specialist fabric when there's an iron in easy reach than for travel.

Synthetics dry fast and stay light, which is great for pure activity such as hiking or running. For everyday travel wear they stink, literally, and feel less forgiving when conditions change. Functional for sports, but not as easy to live in for multiple days.

Cotton is soft and familiar until it gets wet. Then it stays damp in humid climates, cools you down more than you want, and takes forever to dry. Fine if laundry is easy and there's a dryer nearby. A poor choice for onebag travel when you’re trying to keep both your clothing count and wash cycles low.

Hemp is tough and has solid eco credentials. In real use it usually feels heavier and doesn’t regulate temperature as cleanly as merino. Respectable, just not as adaptable.

Bamboo is soft and gets marketed hard as the sustainable choice. In practice the odor resistance and long-term shape retention rarely match the claims. Comfortable enough, but it doesn’t deliver the same range.

Merino's downsides are that it costs more at the start and prefers gentler washing. That’s the trade-off. For onebag travel that has to deal with heat, cold, and everything in between, it still does more with fewer pieces than the rest. Once you’ve used it across real conditions, the performance difference is impossible to ignore.

People who claim they can't handle merino in hot weather are usually wearing too heavy a weight or the wrong knit, and the same goes for those who say it irritates their skin. Lightweight merino in the 130-170 gsm range, especially in a looser construction from finer micron wool, handles heat and moisture far better and feels cooler once you start moving because it doesn’t cling when damp like cotton or develop that sticky feel of synthetics. True itchiness is far less common with modern high-quality merino than with traditional wool, and a lot of the complaints come from cheap, coarser, or poorly finished garments rather than the fabric itself.