Good idea to return an unopened WD Black 4TB for a factory-refurb HGST 8TB?

[VinLAURiA]

I recently just bought a new rig, and the HDD I picked out was a WD Black 4TB drive, model WD4005FZBX. It cost me $175 to get and the shipping was lumped in with all the other parts ($17 for the whole shebang). Now, the drive - like all the other components - is still completely unopened as I'm still waiting on the CPU fan to arrive before starting the build, but while browsing Newegg for something else today, I found a factory-refurbished HGST Ultrastar 8TB that's on sale for $140 until Saturday. Here are the listings for the two drives:

 

WD Black: https://www.newegg.com/black-wd4005fzbx-4tb/p/234-000G-000W6

Ultrastar: https://www.newegg.com/hgst-ultrastar-he8-huh728080aln600-8tb/p/1Z4-001J-008R6

 

Do you think it's a good idea to send back the WD Black and get the Ultrastar? Whatever drive I'm sticking with, I'll be using in tandem with a WD SN750 1TB SSD with a PrimoCache partition (I'm thinking 128GB) to accelerate the HDD. This is the parts list in general for my rig, and I'll be storing my Steam library on the HDD (with games like PlanetSide 2, Distance, various Source engine games, DOOM 2016 to give you an idea of the disc activity) as well as Blender project files and possibly some movies and shows.

[Firewrath9]

Do you need 8TB? if yes, then it's obvious, else, no. I'd also reccommend returning both and getting a pair of ~80-90$ 4TB drives for redundancy.

[VinLAURiA]

Well I guess it's not much a matter of "need" but just getting as high capacity I can get for a reasonable price as I plan to be using the drive for several years. Also to consider is that this would also be $35 less than what I paid for the WD Black despite being double the capacity.