The Intel Core i9-14900 is the objective winner of this comparison, securing victory in nine 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 70% advantage in Max Turbo Power, the superior cache capacity of the Intel Core i9-14900 establishes it as the more capable component across the majority of the evaluated metrics.

Users prioritizing high-capacity cache for complex processing tasks should select the Intel Core i9-14900 to leverage its substantial architectural lead. Conversely, the Intel Core i5-8400 is the appropriate choice for those who specifically require the efficiency profile associated with its 70% advantage in Max Turbo Power. Each processor serves a distinct functional requirement based on these specific hardware differences, allowing users to align their purchase with either cache-heavy performance or power-related specifications.