Which hard disk brand is best? Hitachi?

WD, Seagate, Hitachi & Samsung are all much the same, different users experience different problems & most people have a brand they like. Buy whichever suits you & your pocket. That being said, the WD Blacks are an excellent (if you don't need NAS storage) choice with a decent warranty.

WD quality has been better that's what to do is build hard drives. Hitachi and Samsung dibble and dabble into other focus area's.

WD Blue - good general purpose HDD max 1TB
WD Green - power saving HDD max is 3TB
WD Black - heavy duty
WD Red - NAS and heavy duty

I always go with the WD Blue for my purpose.. I also have them in my NAS too. Might go after WD Red 2x 3TB soon but my needs are just great with what I have on hand. One of my new systems had Seagate in there and it failed in 3 months. Replaced it with
WD Blue 1 TB Desktop Hard Drive: 3.5 Inch, 7200 RPM, SATA 6 Gb/s, 64 MB Cache - WD10EZEX