The Intel Core i9-14900KS is the objective winner of this comparison, securing victory in ten out of fourteen measured specifications. Its most significant technical advantage over the Intel Core i5-8400 is its L2 cache, which is 2033% larger. While the Intel Core i5-8400 maintains a 74% advantage in Max Turbo Power, the superior cache capacity of the Intel Core i9-14900KS establishes it as the more capable component across the vast majority of the evaluated metrics.

Users requiring maximum cache capacity for intensive computational tasks should choose the Intel Core i9-14900KS to leverage its substantial architectural lead. Conversely, those prioritizing the specific efficiency profile associated with the lower Max Turbo Power of the Intel Core i5-8400 will find it the more suitable option. Select the former for high-end performance requirements or the latter if the power-related specification is the primary driver for your specific system configuration.