Well, there are trade offs in both directions. Haskell has a steep learning curve and no clear one choice for concurrency, while Erlang is more approachable, ha

Well, there are trade offs in both directions. Haskell has a steep learning curve and no clear one choice for concurrency, while Erlang is more approachable, has a built-in answer for concurrency, and well-established patterns for building fault tolerant applications at scale. On the other hand, Haskell’s system has more flexibility, offering a few powerful primitives which can be used as building blocks for higher level abstractions. On top of that it is a general purpose language capable of implementing traditional imperative patterns, etc, so you only need to use the concurrency when it makes sense, rather than using it for all stateful and IO operations as in Erlang/Elixir. Its performance ceiling is certainly higher. I don’t think monads in Haskell are a problem except in terms of the learning curve. All in all, which one to use, if either, will depend on the circumstances. But both of them should be a part of any thorough discussion of languages which are “good at concurrency”. ;)