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Intel, in collaboration with Apple, just released the Thunderbolt interface (while under development it was known as LightPeak). It is a 2-channel bi-directional 10Gbps connection over copper, a huge leap in perfmance over anything else. An optical interface is under development for more distance. It supports data transfer as well as providing input to your video display.
The latest MacBook Pro and iMac systems now include this latest and greatest change, and Apple will remove Firewire ports eventually. The connector used is the mini-DisplayPort connector, part of Apple's contribution to this new "Standard". It looks like the first external SSD drive to support Thunderbolt will be from LaCie this summer. Wintel systems and more peripherals to support Thunderbolt are sure to follow.
Currently, eSATA is fast and has less overhead than the others. And provided the PC picks it up as a SATA device, it also will do S.M.A.R.T.
USB 3.0 changes all this though, but not much in my opinion. Not enough to declare itself the speed demon victor anyway.
Also, read this article:
Also, speed is relative to what you'll be doing with it, ie., copying large files vs. small files. Read vs. writes. And that will only happen as fast as the slowest link.
In general though, eSATA is faster than Firewire 800 and USB 2.0. USB 3.0 changes things, but just barely.