Hey there, dodohima!
It really depends on what you intend to use the WD storage drive for. They have different purposes and usually are designed accordingly. I'd definitely not include the
WD Purple as a suitable desktop HDD solution. This drive is a part of our surveillance-class storage solutions. It is mostly used for 24/7 high-definition security systems and spins down regularly due to the IntelliPower RPM that it incorporates. Either way a desktop rig is not a surveillance system, so I wouldn't consider it, if I were you.
The WD Black is our performance drive. It runs with 7,200 RPM and has a 5-year limited warranty. This HDD is designed for high-end gaming and demanding applications in PC rigs. It also comes in numerous capacities to choose from, but I'd recommend to simply check our website for more details on it:
http/products.wdc.com/support/kb.ashx?id=QojWT4
The WD Green is no longer known with that name, though. Recently, this model merged with
the WD Blue. That change intended to simplify the HDD selection by consolidating our mainstream PC product offerings to only the WD Blue family. The ex-WD Green HDDs are now in the 5,400 RPM-class with massive capacities up to 6 TB in size. The well-known WD Blue with 7,200 RPM for everyday computing is still there as well.
I'd suggest you to take a look at the WD Blue's product page as well and check these differences under Specifications:
http/products.wdc.com/support/kb.ashx?id=Odc3W4
Hope this helps you. Keep me posted if you have more questions!
SuperSoph_WD