I cannot say if this is generally true for functional languages but a good comparison of the efficiency of erlang as compared to java can be found by comparing

I cannot say if this is generally true for functional languages but a good comparison of the efficiency of erlang as compared to java can be found by comparing the code footprint of ejabberd, an erlang xmpp server, and openfire, a java xmpp server. The servers are functionally similar yet the source code footprint of ejabberd is approximately 300 files at 5MB and openfire is approximatley 4000 files at 100MB. The erlang server has more then an order of magnitude less code.