Probably JS as the fact that every computer has by default everything you need to execute JS. But there is a bunch of browser stuff you have to worry about before you can do anything with it. I’m not sure how you learn JS before html.

With Python you can do simple command line stuff without having to really know anything else. You can learn one concept at a time.

That being said, people have a lot of familiarity with browsers and it might feel less abstract. JS might a better choice for demystifying coding. Python is probably a better choice for accomplishing anything useful.