p1n3apqlexpr3ss :
Its a bit weird actually
SATA - 1.5Gb
SATA 2 - 3Gb
SATA 3 - 6Gb
USB 2 - 480Mb
USB 3 - 5Gb
Hard to say right now what most companies will use in future, my guess would be USB3.0 however
Theoretically, a SATA connection of equal bandwidth of that of a USB, would still outperform the USB drive.... The reason is simple...
eSATA and SATA (take v3.0/6GBPs in this example vs. USB3.0@5GBPs) drives do not need to do extra conversion sets when reading/writing xferring data. For this reason, eSATA will outperform USB because it does not need to convert data/instruction sets. An external HDD on an eSATA connection xfers the data straight, practically like it was an internal HDD, to the controller chip. A USB external HDD must translate from SATA (the actual HDD itself), into USB coding, which is then read by the USB controller. A USB drive has an extra 'stop' if you will, while an eSATA pipes straight into the system as if it was no different (for practical purposes) than a internal.
The one BIG advantage USB has over eSATA, is that USB generally will not require an external power supply when using a portable external HDD (based on 2.5" drives for example).
So if you are focused straight on performance, eSATA is the way to go IF you can accommodate it. eSATA eHDDs can also be had in general, for less than a USB 3.0 one.