You might have got a Samsung drive that never failed so that's why you think it is the best and it is same about the Seagate as well.
I own a small computer shop, and i sold hundreds only this year. I don't have one myself, i have a laptop now. I did had one on my old system, a 500GB one, it ran like the wind... And very quiet, not like the WD's. I never sent a Samsung back with a warranty issue, but Wd's , especially the 160GB model, the black one, about 20 last year. So i don't sell WD anymore, i hate when customers come back with damaged stuff.
So if I had to choose for myself, i would get a Samsung. But if I were to read what was written on this thread here, i would go for the Seagate. You know, the years they have behind...
Oh, and if you see anything about green on the specs, run. That means slow.