I have all three types of external drives attached to my computer so I just ran a brief test ... here's the result:
USB 2.0 Burst - 29 MB/sec ... Avg 29 MB/sec
FW Burst - 40 MB/sec ... Avg 40 MB/sec
eSATA Burst - 115MB/sec ... Avg 58 MB/sec (this is a SATA 1 drive)
eSATA is clearly superior in all respects.
One of the advantages of eSATA is that is is not seen as a removable device by NT based O/Ses and you can easily install your O/S on an eSATA drive.