Some people have never heard of F# and Rust, too. I certainly didn’t until very recently.
I chose Elixir because it’s a nice, relatively simple, easy-to-learn functional language. F#, on the other hand, is a very large and complex language. I mean, it has 69 + 8 from OCaml + 26 future = 103 reserved words!
Elixir has 18 reserved words.
Rust is an interesting language but I think it will have a tough time breaking into the mainstream. The idea of memory safety and “borrowing” is good but its implementation is rather complicated. I did not find it appealling.
Rust is unproven. Pharo, on the other hand, is a Smalltalk derivative, and Smalltalk has been commercially proven for over three decades, used by hundreds of major enterprises around the globe.