Each company is quite great. The Western Digital Blacks are typically a bit higher performance speed wise, but with a hard drive you won't notice a difference. The Blues are your standard drives, greens are "Power Saving" drives, and red is more for networking/server purposes. The Seagate Barracuda drives are great and sit between the Western Digital Blue and Black performance wise, but typically a fair bit cheaper. Just make sure its the 7200RPM modules.