Got a new external drive today, chose eSATA after seeing that USB3 doesn't handle lots of small files as well as it does large transfers.
(bear in mind both ends are commodity mechanical drives rather than SSD's) A copy of 486GB (63,000 items) is happily progressing at 100MB/sec - makes regular local back-ups a painless process.
I'm sure that could be improved dramatically (say using raid on both ends and 6Gbit SATA) but for simple drive to drive connections eSATA is ideal.