Hey there, Louis531!
The only difference is that the WD1003FZEX from the first link is actually a refreshed model of the WD Black HDD.
Whereas the one from the second reseller is from an older batch. If you have any concerns about either one of them, I'd advise you to
check the warranty on our website as soon as you get them.
I'd recommend you to always check the warranty of any new hardware component that you'd be getting. This is the fastest and surest way to determine how genuine that product is.
Hope this helps. Keep me posted if you have more questions!
SuperSoph_WD