Well, after the OS and a game or 2 the rest of everything will have to go on a HDD.
I have several WD HDD's and only a single Seagate 1TB. The Seagate 1TB compared to the WD1TB, both SATA II, both 32MB cache. Seagate is quite a bit slower than the WD but if you look at an HDTune graph it's really spiky downward. I get 66MB/sec avg. on Seagate and 110Mb/sec on the WD because it doesn't spike nearly as bad.
Out of 6 WD HDD's, never had a failure, bad sectors, clicking noise or toe jam.