Thank you for the comments Tom. I reviewed the same data sheet that you mentioned.

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-black-hdd/data-sheet-wd-black-pc-hard-drives-2879-771434.pdf

And you are right, only the 4TB black or the 6TB blacks are worth buying.
Host to/from drive (sustained)
WD Black 6TB WD6003FZBZ 227MB/s
WD Black 6TB WD6002FZWZ 227MB/s
WD Black 4TB WD4005FZBX 256MB /s
WD Black 4TB WD4004FZWZ 128MB/s
WD Black 2TB WD2003FZEX 164MB/s
WD Black 1TB WD1003FZEX 150MB/s
WD Black 500GB WD5003AZEX 150MB/s

I don’t know from where you get the figure 281.9MB/s. Are all drives in the Black range capable of achieving this speed? It would be helpful if you could provide a reference, please. The WD specifications provide data for sustained transfer rates, not for sequential file reads – I reckon the former is more reliable than the latter. So, according to WD’s own specifications, there’s only *one* model in the range (the WD4005FZBX 4 TB WD Black) that can achieve sustained transfer speeds up to 256 MB/s (less than the 281.9 MB/s figure you provided). The two 6 TB Black drive models are the second fastest in the Black range, maxing-out at 227 MB/s. Also, and importantly, they sell another 4TB Black (WD4004FZWZ) that is an exceedingly poor performer (128 MB/s)

From 2 TB down, the Black drives perform less impressively (on paper). Their WD Blue counterparts should be considered; they are also cheaper, quieter (20-25%) and less power-hungry (>50%), but come with a shorter warranty period (2 instead of 5 years). The 2/4/6 TB Blues are all faster (on paper) than any of the 1/2/4(WD4004FZWZ) TB Blacks. You say the the Blues achieve a speed of 150 MB/s, which is true enough for half the range; the other half are somewhat faster. Comparing the performance per capacity tier, on paper, the 2 TB Blue is faster than the 2 TB Black (max 180 MB/s v 164 MB/s) while the 1 TB Blue is as fast as the 1 TB Black (150 MB/s), and the 4 TB Blue is faster than the 4 TB WD4004FZWZ (175 MB/s v 128 MB/s), but much slower than the 4 TB WD4005FZBX (which is the fastest WD HDD – the only one that can reach 256 MB/s).

The only reason I am documenting all of this is because this page tops google search results and based on your arguably glib #1 recommendation, I was going to buy a WD 2 TB Black. I was surprised and disappointed to learn that this could be a very stupid thing to do – that I wouldn’t get speed up to 256 MB/s, I would get a mere 164 MB/s. I wouldn’t want anyone to do what I was about to do.