The Intel Core i7-14700F is the objective winner of this comparison, securing victory in nine out of fourteen measured specifications. Its most impactful advantage is a massive 1767% increase in L2 cache capacity compared to the Intel Core i5-8400. While the older processor maintains a 70% lead in Max Turbo Power efficiency, the newer model dominates the majority of technical categories, establishing itself as the superior component based on the provided data.

Users prioritizing raw technical capacity and the significant L2 cache advantage should select the Intel Core i7-14700F for their build. Conversely, the Intel Core i5-8400 remains a viable option for those who specifically require the power profile defined by its Max Turbo Power advantage. Your choice should depend on whether you value the expansive cache architecture of the newer processor or the specific power characteristics offered by the older model.