Having used both Ruby and Elixir, this is exact opposite of my experience. I would say Elixir/Erlang is one of the best language from observability/debugging perspective. Immutability, per process heap, ability to trace any module/function call in production (recon), remote shell etc make it trivial to debug most of the issues. I have found memory leak in production from 3rd party library in less than 30 minutes. Just looking at the process list sorted by memory will tell which library is leaking (in majority of the cases), as most of the processes has single purpose.

Strange. I like Ruby, but probably the biggest gain I got from moving to Elixir was the comparative ease of debugging.

Its immutability drastically reduces the search space.

Agree with your point about debugging being easier but in my case I ended up doing a lot of housekeeping for things that are easy in ruby. This time I'm only concerned about the speed of development and ruby to me is the winner