The Intel Core i7-14700K is the objective winner of this comparison, securing victory in ten out of fourteen measured specifications. Its most significant advantage over the Intel Core i5-8400 is its L2 cache, which is 1767% larger. While the Intel Core i5-8400 holds a 74% advantage in Max Turbo Power, the superior cache capacity of the Intel Core i7-14700K provides a more substantial technical lead across the majority of the evaluated categories.

Users prioritizing high-end performance and the benefits of a significantly larger L2 cache should select the Intel Core i7-14700K. Conversely, the Intel Core i5-8400 is the appropriate choice for those who specifically require the efficiency profile associated with its 74% advantage in Max Turbo Power. Your decision should depend on whether your workload demands the expanded cache architecture of the newer processor or the specific power characteristics offered by the older model.