The Western Digital WD Black SN8100 4TB wins in 6 out of 7 comparable specs. Its biggest advantage is Capacity (300% better).
UD90 1TB wins in 1 spec (MSRP: 92% better).
Recommendation
Choose WD Black SN8100 4TB if you want the best overall performance — especially capacity.
Choose UD90 1TB if msrp matters more to you.
