ArchitSahu :
I dont really know the difference between the 2...
If you mean between WD Blue 1TB vs WD Black 1TB? The Blues are made with cheaper parts and just a 2 yr warranty.
Blacks are faster and more reliable and have a 5 yr warranty.
Blues are just for general computing. Blacks have performance and reliability features built in, like Dual Core Processor, High Resolution Controller (HRC), StableTrac Technology, Improved Data Protection: Vibration Control Technology (VCT), Corruption Protection Technology (CPT), NoTouch Ramp Load Technology.
Here in the states at Newegg the Blue is $55 and the Black is $75, but I've seen them carry the Black on promos for $70. It's quite a bit better drive for only $15 - $20 more.