Julia is definitely a step up in data science programming. It's purpose built for data science. I guess that's also the reason why Python has grown more than Julia. The likelihood of someone having worked with Python in an unrelated field means that when starting out in another field, if the Python option exists, they are probably going to take it.

Apart from that, if one is just getting started out in data science and has never really handled a programming language before, Julia is very nice really. And their documentation is pretty damn awesome. And once you get past the performance recommendations I think it gets pretty fast (?). I'm out of my depth beyond a certain point since I've only ever experimented with it.