The Noctua NH-D15 is the objective winner of this comparison, securing victories in two out of three measured specifications. Its most significant advantage is a 14% higher TDP rating compared to the alternative, indicating superior thermal management capacity for demanding hardware. While the Thermalright Peerless Assassin 120 falls behind in total spec wins, it maintains a distinct edge in value, offering a 64% better MSRP that makes it a more cost-effective option for budget-conscious system builders.

Choose the Noctua NH-D15 if your primary requirement is maximum thermal headroom for high-performance components, as its higher TDP rating provides the best cooling potential. Conversely, select the Thermalright Peerless Assassin 120 if you prioritize affordability, as its significantly lower MSRP provides a clear financial advantage. Both coolers offer distinct benefits, allowing you to weigh the importance of raw thermal capacity against the total cost of your build.