With respect to concurrency, after a lot of experience operating async Python services, the thing that I look for is a single, standard, ubiquitous concurrency model. One of the biggest pain points for operating Python systems is some transitive dependency making a synchronous I/O call and blocking the whole event loop, causing timeouts in unrelated endpoints and often bringing the whole system down (healthchecks start to fail because the endpoint is blocked and then the supervisor kills the whole process/pod/etc).

This doesn't happen in Go or (presumably) languages that run on Erlang's BEAM VM because there is no sync I/O (from the event loop's perspective, anyway).