I think I'd only ever choose RoR for a throwaway project, in 2019. I do love RoR and the development experience but Elixir and Phoenix give me almost exactly the same feeling but with WAY better performance and an Immutable/Functional language that results in much cleaner and better code. It's an investment to learn Elixir but it's 100% worth it and honestly I'd choose Phoenix over Rails almost every time.