Hi again, Yeni_09!
Actually the
WD10EZRX model is a WD Green HDD and it does incorporate IntelliPower RMP. However, as @raisonjohn and @USAFRet this drive is meant for secondary storage solution for your massive files. This RPM is not suited for primary OS HDD usage, if that's what you intend to use the drive for. The regular spin-down would result in a very slow boot.
The
WD10EZRZ is a WD Blue though, so it doesn't have IntelliPower RPM! However, this particular model has 5,400 RPM in comparison to its brother the
WD10EZEX model which has 7,200 RPM. I'd recommend you to look at the Specifications and all the available models for the WD Blue here:
http://products.wdc.com/support/kb.ashx?id=KIk8mm
Let me know if you have more questions!
SuperSoph_WD