My original point was about _predictability_ of performance and accidental complexity, that M:N threads with synchronous APIs introduce. But either way, they use way more memory, than necessary and also have to implicitly and explicitly synchronize every little thing, so performance on any meaningful load is going to be very meaningfully worse, than that of event loops.

Still, I want to reiterate, that event loops in modern languages are more about managing complexity, than performance.