Should I choose a different weight class for blend base layers compared to pure merino or synthetic?

Generally, choose the same weight class you would in other materials. However, because blends regulate temperature slightly better than pure synthetics (due to merino's thermoregulation), some skiers find they can go one weight class lighter in a blend compared to pure synthetic. If you typically wear midweight synthetics, a lightweight blend might be sufficient. When in doubt, start with midweight—it's the most versatile option for typical winter skiing.