There are many things that can may be more or less important depending on the personal experience of each one. So for a general audience I tend to show things like:
- achievable performance, of course
- package management
- integration with documentation (help entries and Documenter.jl)
- simplicity of creating, distributing and registering packages
- syntax
- REPL and its features (Pkg and Shell integration), and notebooks
- domain-specific ecosystem: differential equations, non-linear programming, SciML
- plottting etc within the same environment
Each of these things may be available in other languages, but I don’t see any other combining all these features so well.
Then you can go for more language-specific features (multiple dispatch, composability, etc) but IMHO this is harder to understand from a utilitarian viewpoint from start.