Welcome to the community, avidhoonigan!
It really depends on what you are planning to use your storage for, besides the fast boot that comes with both a stock SSD and the WD dual drive.
The WD Black² is designed for any notebook and all-in-one PCs that want the speed of an SSD and the capacity of an HDD. This device comes in the form of a 2.5" internal mobile drive with a height of 9.5mm, making it a perfect fit for most systems. It provides you with the enhanced performance of a 120GB SSD, and the storage capacity of a 1TB HDD, all in one single unit. The biggest difference between other SSDs and the WD Black² is that it gives you that extra data storage, that most users don't want to fill their SSDs with.
If the capacity is not your main concern, then I guess you can go with either.
However, here are a couple of links that will provide you with more details about the WD Black²:
Product page -
http/products.wdc.com/support/kb.ashx?id=8CPEQW
Expected behaviors in a PC -
http/products.wdc.com/support/kb.ashx?id=1Z7kis
How to install it -
http/products.wdc.com/support/kb.ashx?id=rKw49z
Let me know if you have more questions! Hope this was helpful!
SuperSoph_WD