Actors should be in a process no? If it's in a thread then it'll take the main process down with it.

Erlang's BEAM VM every actor is in it's own process. So if something goes bad then it can be restarted via supervisor.

Scala is on JVM and JVM isn't built with concurrency in mind and I think Erlang's BEAM is too good at this. Akka is gimped too, you have to write actor a certain way iirc other wise it takes over the scheduler. BEAM is preemptive, it doesn't matter if you have a for(1) loop, your process/actor can only take some much of the cpu time.

I think hands down Erlang is a really really beautiful language for concurrency. It's syntax is ugly but it's such a small language that does everything you need for concurrency. Scala is just big and there are so many way to shoot yourself in the foot and tons of compromises. I also think implicit type is too magical and shot myself in the foot many time using libraries that use implicit type.