As someone that have spent a lot of time in both Ruby and Python (and specifically a lot of hours in the Python scientific compute stack), I would say that Python is significantly more readable. Python is also significantly easier to teach as opposed to Ruby, especially if the target audience already has a bit of programming experience (from MATLAB, or other courses).

I suspect the main reasons are:

1. Python's guiding philosophy of "There should be one-- and preferably only one --obvious way to do it". With later additions to the language, this is getting less true (3 different ways to format strings, asyncio, type hinting, etc). Some libraries also don't conform to this (matplotlib). That said, it's a lot better than the Ruby code I've encountered, which is like the wild west.

2. Python's syntax is reasonably simple to teach. The object model could be condensed into something very simple if you don't need a lot. With very basic knowledge, you can go a long way. Ruby's a bit more chaotic with things like inheritance, extend, and include; proc, block, lambda; having to use attr_accessor; syntax things like a = b could be a function call or not; if/unless; and many more things that are confusing.

3. Even basic things like loops in Ruby is not idiomatic as it wants to apply a function/block instead. Beginners, especially those with a bit of background, like their loops better than functional programming.

As I've spent many years working on Ruby code base I still get lost all the time. Python in my experience has been a lot better, although recent Python versions have regressed a bit as it introduced more syntax to do the same things.