[stass]

There are at least 2 major differences relevant to message processing: 1) Erlang runs in a VM which provides preemptive scheduling and builtin message flow control (sending a message costs proportional to the receiver mbox size) 2) Unlike other VM languages, Erlang VM provides per-process heap, which helps to eliminate VM pauses. None of JVM based solutions can provide low latency processing unless you manage the heap by hand.

As people said before, Erlang combines several traits in a nice package, which is hard to beat.

There are other differences in the language as well. Bing a functional language with TCO it allows you to implement a lot of algorithms which will be cumbersome in imperative languages. Powerful pattern matching capabilities allow one to structure the program in a clean way, and pattern matching on binaries makes most binary protocol parsers one-liners.