For some mathematical work, going from Mathematica to Python/Julia/Octave/Scilab would be a significant step backwards.
This is coming from a pythonista btw. To each their own. Python is a better scripting language, but Mathematica is a better analysis language for a lot of things. Python is catching up in a lot of ways though with Numpy and Tensorflow. I'd say Python's Tensorflow is a lot more mature than Mathematica's neural nets, but Mathematica's symbolic math seems to be world class.
This is coming from a pythonista btw. To each their own. Python is a better scripting language, but Mathematica is a better analysis language for a lot of things. Python is catching up in a lot of ways though with Numpy and Tensorflow. I'd say Python's Tensorflow is a lot more mature than Mathematica's neural nets, but Mathematica's symbolic math seems to be world class.