Erlang is much easier than Haskell. Erlang is a pretty good gateway into Haskell, too; if you know Erlang, you have fewer things in Haskell throwing you for a loop. It's the road I travelled, and Haskell is certainly easier to use when you've already gotten immutability, and writing useful programs with immutability, already nailed down, so you're just learning the things specific to Haskell rather than trying to swallow an entire major new paradigm at once.