Comparing to Ruby is apples to oranges because Ruby's concurrency and operational foundation is weak. The better comparison is Erlang/OTP vs JVM, where JVM gets the edge on optimized performance, and Erlang/OTP gets the edge on concurrency & tooling. The appeal for Scala folk would be if you don't care about the JVM compatibility or raw performance, and want an opinionated ecosystem built from the ground up around the actor model.
Elixir brings style to Erlang/OTP.
Comparing to Ruby is apples to oranges because Ruby's concurrency and operational foundation is weak. The better comparison is Erlang/OTP vs JVM, where JVM gets the edge on optimized performance, and Erlang/OTP gets the edge on concurrency & tooling. The appeal for Scala folk would be if you don't care about the JVM compatibility or raw performance, and want an opinionated ecosystem built from the ground up around the actor model.