I personally hate seagate. At least I can say their Barracuda line is trash after RMAing a barracuda 3 times I gave up.
For western digital I have used a Caviar SE16 which still works today, and I have a set of raid edition 3s and a single caviar green 2TB. No Western Digital drive has failed on me to date. Seagate has failed many times.
I just got my hands on 2 spinpoint f3s. I don't have past experience with samsung drives so I can't say but on paper the spinpoints are very good bang for you buck and faster than the caviar and raid edition drives. I mainly got them because they cause less vibrations than my RE3s.
I like Seagate. I have had very good experiences with them over the years.
Anyway, nowadays I would go for the Samsung Spinpoint F3 HD103SJ 1TB SATA 3Gb/s 32MB-cache or the WD Caviar Black 1TB WD1002FAEX SATA 6Gb/s 64MB-cache. I recommend you to go for a 1TB HD (they have the best ratio €/Gb).
Another good option would be the Seagate Barracuda 7200.12 ST31000528AS 1TB SATA 3Gb/s 32MB-cache.