"So there has to be a really, really, really good reason to choose that particular programming language"
If it is an obscure language yes, you'd ned very good reasons, but if it is any of the common languages then what you pick will be less a choice and more like something automatically determined by whether there's any existing library you particularly want to use (for example Fortran is still popular with X-ray astronomers specifically because someone wrote a bunch of x-ray spectrometry libraries for it, Python is good if you want to make use of Tensorflow for AI stuff or use stuff derived from Blender to handle 3d graphical functionality), or by what you're already most familiar with (and can thereby reuse sections of code and functions from things you've written before).