It just have so much depth with concurrency. The actor model is amazing and easy to think about too.
I'm not entirely sure they overlap completely but the concurrency model is superb. I will probably only use Elixir for web application from now on (unless they don't have packages for certain API). Chris have made web development possible and many awesome people have contributed (POW package is just lovely).
You're praising Erlang's concurrency model, there's no such thing as Elixir concurrency model.
But it's also inescapable to ignore Erlang when you dive deeper into the actor model. Several good actor model books are Erlang only. Unfortunately many people, including myself, ever actually do anything hardcore with Actor Model. There is a good blog post about several skill stages of erlang/elxir and OTP was at the very top in term of few people actually uses it. I can't recall it the author =/.
Actually, I like Elixir package management system and command line tool is much better. They recently have the release command line tool. Elixir have several more differences?