Hi,
Mark's reply came in while I was typing this...
I took a quick look at the specs to compare against the Seagate drive, and there is very little to choose. The have the same rotational speed, the same cache size, and the same interface speeds. At the extremes there may be a few differences, but I doubt they would make any difference at all in the Phatbox application.
As Mark says, warranty may be more significant, although in practice, three of five years is probably academic.