Elixir has more syntax to learn than Erlang. You could learn just about everything there is to know about Erlang syntax in a half hour, with the exception of a few advanced features like list comprehensions.

Elixir's syntax is much more familiar to most developers. Most consider this a good thing; I'm biased because Erlang's unusual syntax helps me think differently. If I write something that looks like Ruby, I tend to think like Ruby.

Knowing Erlang can only help with Elixir, but it's not necessary. There are probably more jobs with Elixir these days, which is a good thing. I guess I'm not really helping, so I'll shut up.