WD hard disks post mortem

I have heard that there is not much technical difference in WD range of hard disks actually and almost all disks are identical inside (There is no marked difference in quality of PCB's of basic WD Blue and Data center grade Gold as well)

Those experts who have done research on head type /quality and platter quality testing might shade light on this.
Unlike WD ,Toshiba Enterprise is having high quality build and hugh differnces in design as compared to desktop disks.
Personally I have found Toshiba highly reliable .Not a single failure case is reported from nearly 400 hard disks I have sold in last 6 years.
With departure of Hitachi which was another rock solid brand only Toshiba has remained trustworthy brand.
Pls.comment.