If you don't go for a SSD then in my experience the Samsung Spinpoint is much quieter than the WD Caviar Black. I have a 1 TB in both.
The Samsung is suppose to have an acoustically designed casing to reduce Hdd noise.
For me, hard drives are obsolete now.
The SSD is faster and it has a long enough life time so it wins.
My next machine will have 3 solid state drives as follows :
1. Operating System and applications.
2. Sample libraries.
3. Cubase projects.