i.Link is simply Sony’s name for the 4-pin unpowered implementation of the firewire standard. Sony didn’t create this 4-pin mess but they sure market the hell out of it. The smaller size makes it ideal for making things smaller but sucks because it requires and device using 4-pins to supply their own power.
So, any firewire hard drive will work with the i.Link port but that device will need to provide its own power. So, if you’re buying one of those 3.5” based hard disks then they will already come with some sort of power unit. 2.5” based hard disks can generally be powered through the USB port although some may still require external power.
So, in terms of speed, they are nearly identical in real world performance. USB drives do tend to be more dependent on the host CPU since it’s a “dumb” interface. Firewire typically has much lower CPU utilization during transfers.
So, if you need something that’s small and portable then a 2.5” based one with a USB2 connection would be ideal since you only need to carry a USB2 cable. If you don’t need to be mobile with this external drive and want something big like a 3.5” based one then it really doesn’t matter since you’ll need to hook it up to external power and performance is similar with either interface.
In the end, the best thing to do is to buy a dual interface device. I do that for my 3.5” and 2.5” based external storage. It costs a little more but you get peace of mind that you can connect to anything. :wink: