Multiple dispatch and meta programming are both wonderful, irrespective of speed benefits.

For example, compare linear algebra syntax in Julia with those in R and Python.

Plus, the flexibility of multiple dispatch applying equally well to any of your own types really makes it feel like you can do anything in Julia.

Metaprogramming, writing code that writes code, can take a while to get used to. But is extremely powerful.

A final point I will make is comparability of Julia code. If you want to for a Bayesian model or solve a differential equation in Julia, you can mix your own types and code and any generically written library code at will, and it will often just work. In R, you're not likely to find that; your Stan code can't call R functions you've written or those from your favorite libraries.