WD is No. 1
I've never liked Seagate, due to high failure rates, and even more so since they took over Maxtor. I've NEVER had a Western Digital hard drive fail, compared to about 25 Seagate/Maxtor ones, and that's NOT including customer ones. The Maxtor 2F0L0 20GB drives were known to be crap, I had bucketloads of them die, either electronically, or because of bearing failure. They only had 2 platters, were thin and quiet, but failure prone.
As far as I'm concerned, from my experience (I'm a repair company owner), Western Digital and Hitachi are my top two, and the only ones that go in any of my machines or company servers. When I stick a WD in a computer, I am assured that it isn't going to come back for HD replacement, only maintenance and regular backup, as my customers entrust me to do backups for them on site.
If WD start to sell SSD's mainstream, and eventually as cheaply as their mechanical drives, I won't hesitate to use them. Their recent pricing of their new 1TB 2.5" drive at around $179 has surprised me, too.