You should read the paper, but Julia's also a really nicely designed language in general. It's hard to communicate how great multiple dispatch + a powerful type system is without trying it out (though, again, the paper does a good job), but yeah, it really helps you get a lot of generality as well as performance. When you use Cython, you immediately lose that generality.
Then there's the really powerful metaprogramming capabilities, which are absent from the languages you've mentioned. I can't emphasise it enough: the paper this comment thread is about does a great job of explaining why these things are compelling.
Also, you may be interested in [1], an argument that language performance is valuable even if you don't need it yourself.
[1]: https://medium.com/the-julia-language/performance-matters-mo...