The major problem, without any measurement and just guesswork, is that you have a larger allocation overhead in Erlang. Not only do you need the process control

The major problem, without any measurement and just guesswork, is that you have a larger allocation overhead in Erlang. Not only do you need the process control block for the process, you also need to go to the memory subsystem and grab a heap for the process. In the Go variant, you are allocating out of the same heap and you can usually avoid some allocation there because everything you allocate is used. Not so in the Erlang system. Were these processes/goroutines to do anything more complex, then the difference goes toward zero. But the constant overhead at the lowest level is probably higher.