1tb SATA Seagates bad in HW raid 5?

"WD's perform way better" - a typical fanboy comment.

I can tell you from my experience because I have a 3-drive Seagate 500GB 7200.11 Raid 5 array on a 3ware 8port Sata controller. The 1TB Seagates perform almost identically to the 500GB.

The controller will be your limiting factor for Raid 5 because it must calculate the parity for writes. With my 3ware Raid 5 setup, I get 130-80MB/s sustained writes and 200-140MB/s reads in order from 0GB to 930GB(which is why speeds slow). If you want better speed, go with the 1.5TB as they are about 20% faster than the 1TB & 500GB 7200.11s. I can't find my saved benchmarks for when I first set this up, but I thought I was able to get 150MB/s writes at the start.

The Raid controller must have a dedicated cpu which most controllers under $300 do not have. Preferably, one with Intel's IOP 34x. Even if most drive use will be reads, writes will bog it down more or less depending on the controller cpu.