For the benchmarks done in the paper, elixir should basically benchmark identically to erlang, since if there's any performance regression, it's a very thin wrapper.

I doubt crystal is mature enough in its multithreading model (which is still nascent, and IIRC not fully supported in the current rev, and inherited from ruby's in concept) to perform well at all in this. Erlang, Go and Akka were all conceived of specifically to handle multithreaded connections.