'taint a contest. With Seagate you have a "50/50" chance of getting a crap noisy motor. Plus it has no AAM nor APM. If you want the fuzzy feeling of a five year warrany plus the highest reliability rating then go for a WD3200YS. Dunno if they have caught up with the rest of the industry in actually releasing higher areal densities; ergo two-platter in this capacity (they announced last July but have not heard any confirmations from in ze wild).
Samsung have their new high-density PMR HD321KJ out but alas they also suffer a "50/50" motor problem although not with noise but vibration.
So, perhaps the best of all is Hitachi from the T7K500 series as they are not lacking in any area, save the option of a five year warranty which, all things considered, is the easiest discarded feature or characteristic when the choice must be made.