Respectfully, I'm not sure I buy this comparison. Yeah, CoffeeScript adds some cleaner syntax and OO niceties onto JS, it's still basically just a higher level abstraction that get boiled down to JS. Elixir is a multi-paradigm language that that gets turned into the same type of byte code that Erlang does and is interoperable with Erlang. Its more like jRuby and Java both living on the JVM and being able to call Java code in jRuby, or maybe its a bit like ClojureScript and Clojure?