I think Ruby is the ideal language for AoC:

* The expressive syntax helps keep the solutions short.

* It has extensive standard library with tons of handy methods for AoC style problems: Enumerable#each_cons, Enumerable#each_slice, Array#transpose, Array#permutation, ...

* The bundled "prime" gem (for generating primes, checking primality, and prime factorization) comes in handy for at least a few of problems each year.

* The tools for parsing inputs and string manipulation are a bit more ergonomic than what you get even in Python: first class regular expression syntax, String#scan, String#[], Regexp::union, ...

* You can easily build your solution step-by-step by chaining method calls. I would typically start with `p File.readlines("input.txt")` and keep executing the script after adding each new method call so I can inspect the intermediate results.