Mathematica is awesome for weird, one-off tasks in fields that I'm unfamiliar with, since the documentation is excellent, and the functionality is really broad (so I don't need to figure out how to install a specialty program for every one-off task). But for fields that I'm experienced with or tasks that I'm planning on running frequently, I'll usually just use Python, since most of the Python libraries have more functionality and run quicker than Mathematica.

(Mathematica is of course much better than Python at symbolic math, but this isn't what you are asking about)