Perfomance difference between dbmail-smtp and dbmail-lmtp

Hi,

What's the perfomance difference between dbmail-smtp and dbmail-lmtp? In 
every case MTA need to create another process: dbmail-smtp connects 
directly to database, dbmail-lmtp connects to dbmail-lmtpd (which is 
alredy connected to database) on TCP socket.
Is dbmail-lmtp with message processing more faster than MySQL direct 
connection? Why?
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Thanks,
Eugene Prokopiev