[rudyonrails14]

If going with the web, I'd go with JavaScript, to a degree you have to learn it anyway. Python and Ruby are both relevant for web as well. Rails vs Flask/Django - both will get the job done, plenty of use cases of major corporations using one or the other.

If you're doing DevOps, you should probably learn both.

Everything else, which is more backend, APIs, data, data science, AWS, Google Cloud, Big Data databases, etc - Python over Ruby. You may want to consider Java here tho depending on how much performance is required due to many of those aforementioned Big Data platforms having the JVM underneath the hood.

So all things being equal, Python, and then for all things not being equal, Python.

[mercer]

To add to that in regards to web development: you're going to need JS anyways much of the time, so learn it. You Don't Know Javascript and Eloquent Javascript are respectively good starting points and good but tough starting points.

But as of yet there's nothing in the JS ecosystem that compares to Ruby on Rails or Django for back-end stuff, so it's worth learning one or both those two as well.

For finding work: learn both, or pick the one that is more popular in your desired field, geographic location, etc.

For improving yourself as a programmer: go for Python first but learn both (good introduction to how programming languages are both different and alike). If you can't be bothered by or interested or learning both, reconsider your field of work, because both are fun.

For anything else: if you're capable of weighing the pros and cons of either in regards to support (hiring coders), project size, level of complexity needed etc.: Python strikes me as the slightly safer / more robust choice, especially in academia, but I'm not confident about recommending either one primarily.