The faster devices generally vibrate more and give off more heat, which might make them unsuitable for mass storage (i.e. in a NAS box or other multi-drive arrangement). The difference might technically even invalidate warranties.

They also draw more power, which might mean they simply don't work properly in some low-power devices, or mean that any UPS someone might have one connected to will not last as long as they expect during a power interruption.

> Isn't higher RPM better

WD Red is marketed for NAS/storage, where it's not uncommon to have 4/8/12/16 drives in the same chassis where noise/heat becomes a very different problem. It turns out that the drives generated the same heat and consumed the same power as 7200RPM drives, while the data sheets were outright lies and BS. WD decided on double down on the BS for several months, and only recently released new SKUs where the specs matched the marketing.

It’s correct, and higher is better, 7K2 is faster and often longer lasting somehow. Generally better built. Downsides are noise, power draw and thermal.

They sourced drives from former HGST under WD but 5K4 we’re not available so marketing rebadged 7K2 as “5400rpm-class” and lucky buyers were hit with better performances.

> lucky buyers were hit with better performances

Sort of. The WD Red drives outperformed actual 5400 drives but underperformed other 7200 drives by a large margin (180MB/s vs. 230MB/s), while not necessarily offering heat or noise benefits that matched. My current 8x8TB WD Red Unraid build will likely be the last WD drives I buy for a long time.

No, right way around.

Less noise and usually higher durability.

WD cut down the number of real SKUs and then slowed down a 7200 RPM drive in firmware calling them "5400rpm class"