Well both have pros and cons
From what I can gather from other threads and online Segate one is better at speeds but Segate is not very good in case of RMA and if you go for WD then speeds will take a hit but their RMA and ASS is real good.
OT - Damn its weird to always write "That company has nice ASS", gives me other feelings. But who has time to complete the abbrevations.
Please don't create multiple threads for same reason.
So I guess you are going for WD right ??
Seagate for speed.
WD for reliability and after sales service.
I choose WD.