One area that would be interesting to compare is deployment options.

Case study of:

• How Discord Scaled Elixir to 5,000,000 Concurrent Users
• Using Rust to Scale Elixir for 11 Million Concurrent Users

Perhaps?

Another subject can be Witchcraft and Category Theory

I recently supervised a bachelor thesis about the implementation of a protocol stack in Elixir.

A comparison to an existing C-implementation was part of the work and very interesting.
Readability (clear flow, declarative to the point that you could just write off parts of the industry norm into code) and testability were far better with Elixir.

What distinguishes Elixir and all other languages in the BEAM ecosystem is the BEAM runtime, and it’s guarantees for building reliable concurrent, distributed and fault-tolerant systems. This comes not as an afterthought, but instead as a requirement of Ericsson when asked Joe to design the language.

As far as I am aware the BEAM may be the only language designed from scratch with this things as a requirement.