A massive point for me missing in this article is the experience of having to wait for Crystal to compile - especially for development, this sucks. Try timing puts "Hello, world" on both:
~ % cat test.rb
puts "Hello, world"
~ % time ruby test.rb
ruby test.rb 0.03s user 0.05s system 25% cpu 0.312 total
~ % time crystal run test.rb
Hello, world
crystal run test.rb 1.48s user 1.09s system 72% cpu 3.559 total
I find this perspective kind of funny, because every medium-sized Ruby project I've worked on takes 10+ seconds just to load and start rspec (before it runs any of my tests) or a REPL.
Because of this, working with Ruby is actually substantially slower than working with a similarly sized Go project, in my experience, even though Go theoretically has the disadvantage of needing to compile things before running them.
Plus, Go's type system will catch tons of bugs that Ruby optimistically treats as "maybe you meant to do this". Obviously Rust's type system is really awesome, but Go's is still really helpful, while compiling much faster than Rust.
Since Rust and Crystal are both LLVM-based, I would guess that Crystal's compile times also tend to be a bit painful on medium-sized projects, like Rust, but I've never actually used Crystal for anything more than "Hello, World".
(I've been paid to work full time with Ruby, Rust, and Go over the years, and they each have pros and cons, but I just don't think I would ever personally choose Ruby for any new project in 2020, if I had a say in it, given how great Go is for web development.)
