I like Crystal, but I personally see it more as a tool for number crunching. I think I read that Soundcloud are one of its early adopters.
With regards to performance - what do you mean specifically? Phoenix pre-compiles/caches templates by default so on serving pages it is incredibly fast (micro seconds). Thanks to the BEAM, it also offers massive concurrency and parallelism along with fault tolerance (there’s no point being able to serve so many requests if your system fails because of a problem).
I heard Crystal folk say they want to implement something like the Actor model that Erlang has, but I’ve also heard @joeerl (I think in relation to Java stuff) say something along the lines of that sure, anyone can implement a similar model to Erlang - but then they’ll need 20 years to get to where Erlang is at. Erlang wasn’t just built and then stayed the same - it was worked on, tweaked, enhanced over a couple of decades to get it to where it’s at today 
There’s also another thing worth mentioning. I think for anything to be ‘better’ than Elixir and Phoenix, after having been inspired by it, is for those trying to better it to actually know more about it than on a superficial level… because the more you know about Elixir and Phoenix the more you realise what’s truly special about them 
(and by that stage, they’ll probably want to stay with Elixir 
).
