Personally, I only use WD Blacks. Is it worth $25 for 2.5x more warranty, well that's up to you.
Seagate (and samsung) are able to offer their drives at a lower price because they give you less warranty. After 2yrs if it dies, it's your problem, you have to buy a new one.
WD charges more, but they will warranty your drive for 5yrs. The good thing about that is say in 4yrs your WD 1TB drive dies, you send it in and likely your going to get a 2 or 3tb drive as a replacement because 1tb drives won't be made anymore.
I plan to buy a SSD for boot drive and programs, so no Raid
but the question still remains
beside warranty, what about speed?
is WD much faster because of its cache or there is no noticeable improve in everyday use??
and I just heard about "density platters"
are they different in this field?