Of course I'm comparing them. Threading and async are two solutions to the same problem: How do you write high performance event driven systems like network services? How do you solve the C10K problem (or more recently the C10M problem)?

If you use a thread per connection (or green threads like Go), you don't also need async. If you have async (eg nodejs), you can get great performance without threads. You're right that they can also be combined - either within a single process (like tokio in rust). Or via multi-process configurations (eg one nodejs instance per core, all behind nginx). But they don't need to be. Go (green threads) and Nodejs (async, single threads) both work well.

Of course we're comparing them. We all want to know who wore it better