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You are correct I think (no personal experience with comparing). According to John Barklow the Sitka big game line manager, which I referenceD earlier because I have listened to him on several podcast and he explains merino vs synthetic better than anything I’ve heard.
The good synthetics move the moisture away from your skin so fast that you can feel slightly cool/cold for a short period of time do to an evaporative type cooling process but it only last a short period of time. You can help negate those effects by adding a puffy as soon as you stop.
With merino you will stay warmer when you sweat but you will stay wet for much longer. So if you don’t mind being wet/damp then go merino but you can stay just as warm with the synthetics.
You can also add a synthetic over the merino which will help pull the moisture from the merino to the outer layers some.
Personally, as of now I have all merino base layers but they are just next to skin and very light, I add synthetic on top if needed . I am looking at trying synthetics as next to skin/base layer but haven’t yet.