Both merino and synthetic base layers wick moisture and dry faster than cotton, but they trade off in different ways.
Merino resists odor remarkably well, making it the choice for multi-day trips, and it feels warm across a wide temperature range. Synthetics dry faster, cost less, and stand up to heavy abrasion better than wool.
Many hikers keep both: merino for backpacking and cold days, synthetic for high-output efforts where speed of drying matters most.