No, you brought that (green threads implication) into the discussion. My whole point is that you're making an implication based on that distinction and that's just not true.

Both Erlang and the JVM have to map lots of actors to a number of hardware cores. Lightweight threads of various sorts on top of a smaller number of hardware processes/threads is the same for both. Both Erlang and the JVM use an MxN model. You're last sentence seems to imply that you believe something different.

They make some different tradeoffs because of their goals (coordination vs. general purpose) that has some real implication as to solving particular problems more or less easily. I.e., if you're doing coordination dominated systems then Erlang is easy and the underlying performance loss due to other implementation issues is mitigated. On the other hand, if you have lots of data and computation, then Java's solution will blow Erlang away. The real world is about understanding, choosing, and managing the real tradeoffs -- not pushing some theoretical ideal.