The Samsung 990 Pro 4TB with Heatsink is the objective winner of this comparison, having secured two spec victories compared to zero for the Western Digital WD Black SN850X 4TB. The most impactful advantage offered by the Samsung 990 Pro 4TB with Heatsink is its sequential write speed, which is 5% better than that of its competitor. While the two drives share identical specifications across five other categories, this performance lead establishes the Samsung drive as the superior option.

Users who prioritize the highest possible sequential write performance should choose the Samsung 990 Pro 4TB with Heatsink for their storage needs. Conversely, because the Western Digital WD Black SN850X 4TB matches the Samsung drive in five out of seven categories and lacks any unique spec advantages, it remains a viable alternative for users who find the two drives functionally equivalent in most measured areas. Both options provide identical capabilities across the majority of the evaluated technical specifications.