[erszcz]

Erlang and Elixir are way more "the same thing" than, for example, Java and Clojure are. The summary that "they both run on the same VM" is very general and elides a lot of details.

Elixir, on the one hand, is a new library and tool ecosystem. It's hard to compare libraries, but tool-wise, Elixir wins simply because it has them. Erlang has been underdeveloped in this aspect for years and it's not changing very fast.

Syntax wise they are pretty different, but it's trivial to use Erlang libraries from Elixir (not as easy and not always possible the other way around) and there's not feel that they're designed with different principles or feel foreign. Moreover, some standard Elixir APIs are simply old Erlang libs dressed up in slightly better clothes.

On the other hand, it's just the syntax which differentiates Elixir (the language, not the ecosystem) and Erlang. Only the compiler frontend is new in Elixir, from a certain point (an Erlang abstract syntax tree) it's Erlang all the way down to the bytecode/VM-executable code level.