[rdtsc]

It runs on Erlang's VM. So there are chances if you pick one up or another you'll be able to at some level inter-operate.

It is up to you, try one and another one. Some people have big issue with Erlang's syntax. I actually kind of like it, so I prefer Erlang.

Others find Elixir more approachable, it reminds them of Ruby for example. Elixir has macros so you can do some nifty things with them. Those kind of blow my mind when I read them so I am afraid I would get too "clever" with them.

You can call Erlang from Elixir fairly easily so you can take advantage of libraries you find for Erlang.

So kind of up to you. Whatever you like or whatever gets you more productive and interested.