As you said though, config/prod.exs no longer works for mix run with config tuples so you don’t have two files, but you don’t have the same functionality. There is nothing stoping you from doing the same with distillery config and having a single file. 
Also, it is worth saying the reason distillery went with two config files (afaik) is to separate compile time from runtime config. But I don’t think this is a 
or a 
for any because you can run into issues in both approaches (and this is mostly on Elixir rather than those libs).
I can see however the convenience of the system API. Thanks for replying!
