Actually it is not a good comparison. scalac compiles directly to byte code that runs on the JVM. Scala has pretty different semantics from Java. Whereas Elixir is compiled to the Erlang AST - a pretty high-level data structure - and then the Erlang compiler is invoked on this structure to compile byte code for BEAM. So whereas Scala can do things Java can't do (such as closures on Java 6), there really is nothing Elixir can do that Erlang can't.

The fact that Elixir has the same semantics is really a good thing, because it makes it much easier to learn both languages at the same time and that is still pretty much essential in my opinion, if you want to become productive in Elixir.