Yeah, talking speed in the manner of C1M sorts of things. Server stuff - where python tends to be rather than GUI side. It's demonstrably faster for IO to not be context switching with threads -- but if threads were equal weight to events, I don't the event programming style being more programmer productive than the threaded style. I can see where events are useful in a GUI context, but UI Thread + thread pool dispatch still works well, if your framework supports it.

Just this week, I got to the bottom of a performance issue in django because the developers were using async, and then doing eleventy billion db queries to import a big csv, thereby blocking all other requests.

One of the questions I ask on our programming interviews is "how would you make this (cpu bound) thing go faster" -- Async is definitely a low quality answer to that, when things like indexing or hash lookup vs array scan are still on the table.